Getting Started

The Parse platform provides a complete backend solution for your mobile application. Our goal is to totally eliminate the need for writing server code or maintaining servers.

If you’re familiar with web frameworks like ASP.NET MVC we’ve taken many of the same principles and applied them to our platform. In particular, our SDK is ready to use out of the box with minimal configuration on your part.

If you haven’t installed the SDK yet, please head over to the QuickStart guide to get our SDK up and running in Visual Studio or Xamarin Studio. Note that our SDK requires Visual Studio 2012 or Xamarin Studio and targets .NET 4.5 applications, Windows Store apps, Windows Phone 8 apps, and Xamarin.iOS 6.3+ or Xamarin.Android 4.7+ apps. You can also check out our API Reference for more detailed information about our SDK.

Parse’s .NET SDK makes heavy use of the Task-based Asynchronous Pattern so that your apps remain responsive. You can use the async and await keywords in C# and Visual Basic to easily use these long-running tasks.

Objects

The ParseObject

Storing data on Parse is built around the ParseObject. Each ParseObject contains key-value pairs of JSON-compatible data. This data is schemaless, which means that you don’t need to specify ahead of time what keys exist on each ParseObject. You simply set whatever key-value pairs you want, and our backend will store it.

For example, let’s say you’re tracking high scores for a game. A single ParseObject could contain:

score: 1337, playerName: "Sean Plott", cheatMode: false

Keys must start with a letter, and can contain alphanumeric characters and underscores. Values can be strings, numbers, booleans, or even arrays and dictionaries - anything that can be JSON-encoded.

Each ParseObject has a class name that you can use to distinguish different sorts of data. For example, we could call the high score object a GameScore. We recommend that you NameYourClassesLikeThis and nameYourKeysLikeThis, just to keep your code looking pretty.

Saving Objects

Let’s say you want to save the GameScore described above to your Parse Server. The interface is similar to an IDictionary<string, object>, plus the SaveAsync method:

ParseObject gameScore = new ParseObject("GameScore");
gameScore["score"] = 1337;
gameScore["playerName"] = "Sean Plott";
await gameScore.SaveAsync();

After this code runs, you will probably be wondering if anything really happened. To make sure the data was saved, you can look at the Data Browser in your app on Parse. You should see something like this:

{
  "objectId": "xWMyZ4YEGZ",
  "score": 1337,
  "playerName": "Sean Plott",
  "cheatMode": false,
  "createdAt":"2022-01-01T12:23:45.678Z",
  "updatedAt":"2022-01-01T12:23:45.678Z"
}

There are two things to note here. You didn’t have to configure or set up a new Class called GameScore before running this code. Your Parse app lazily creates this Class for you when it first encounters it.

There are also a few fields you don’t need to specify that are provided as a convenience. ObjectId is a unique identifier for each saved object. CreatedAt and UpdatedAt represent the time that each object was created and last modified in your Parse Server. Each of these fields is filled in by Parse, so they don’t exist on a ParseObject until a save operation has completed.

Data Types

So far we’ve used values with type string and int assigned to fields of a ParseObject. Parse also supports double, DateTime, and null. You can also nest IDictionary<string, T> and IList<T> objects to store more structured data within a single ParseObject. Overall, the following types are allowed for each field in your object:

• String => string
• Number => primitive numeric values such as doubles, longs, or floats
• Bool => bool
• Array => objects that implement IList<T>
• Object => objects that implement IDictionary<string, T>
• Date => DateTime
• File => ParseFile
• Pointer => other ParseObject
• Relation => ParseRelation
• Null => null

Some examples:

int number = 42;
string str = "the number is " + number;
DateTime date = DateTime.Now;
IList<object> list = new List<object> { str, number };
IDictionary<string, object> dictionary = new Dictionary<string, object>
{
    { "number", number },
    { "string", str }
};

var bigObject = new ParseObject("BigObject");
bigObject["myNumber"] = number;
bigObject["myString"] = str;
bigObject["myDate"] = date;
bigObject["myList"] = list;
bigObject["myDictionary"] = dictionary;
await bigObject.SaveAsync();

We do not recommend storing large pieces of binary data like images or documents on ParseObject. We recommend you use ParseFiles to store images, documents, and other types of files. You can do so by instantiating a ParseFile object and setting it on a field. See Files for more details.

For more information about how Parse handles data, check out our documentation on Data.

Retrieving Objects

Saving data to the cloud is fun, but it’s even more fun to get that data out again. If the ParseObject has been uploaded to the server, you can retrieve it with the ObjectId using a ParseQuery:

ParseQuery<ParseObject> query = ParseObject.GetQuery("GameScore");
ParseObject gameScore = await query.GetAsync("xWMyZ4YEGZ");

To get the values out of the ParseObject, use the Get<T> method.

int score = gameScore.Get<int>("score");
string playerName = gameScore.Get<string>("playerName");
bool cheatMode = gameScore.Get<bool>("cheatMode");

The four special values are provided as properties:

string objectId = gameScore.ObjectId;
DateTime? updatedAt = gameScore.UpdatedAt;
DateTime? createdAt = gameScore.CreatedAt;
ParseACL? acl = gameScore.ACL;

If you need to get an object’s latest data from Parse, you can call the FetchAsync method like so:

await myObject.FetchAsync();

Updating Objects

Updating an object is simple. Just set some new data on it and call one of the save methods. For example:

// Create the object.
var gameScore = new ParseObject("GameScore")
{
    { "score", 1337 },
    { "playerName", "Sean Plott" },
    { "cheatMode", false },
    { "skills", new List<string> { "pwnage", "flying" } },
};
await gameScore.SaveAsync();

// Now let's update it with some new data.  In this case, only cheatMode
// and score will get sent to the cloud.  playerName hasn't changed.
gameScore["cheatMode"] = true;
gameScore["score"] = 1338;
await gameScore.SaveAsync();

The client automatically figures out which data has changed so only “dirty” fields will be sent to Parse. You don’t need to worry about squashing data that you didn’t intend to update.

Counters

The above example contains a common use case. The “score” field is a counter that we’ll need to continually update with the player’s latest score. Using the above method works but it’s cumbersome and can lead to problems if you have multiple clients trying to update the same counter.

To help with storing counter-type data, Parse provides methods that atomically increment (or decrement) any number field. So, the same update can be rewritten as:

gameScore.Increment("score");
await gameScore.SaveAsync();

You can also increment by any amount using Increment(key, amount).

Lists

To help with storing list data, there are three operations that can be used to atomically change a list field:

• AddToList and AddRangeToList append the given objects to the end of an list field.
• AddUniqueToList and AddRangeUniqueToList add only the given objects which aren’t already contained in an list field to that field. The position of the insert is not guaranteed.
• RemoveAllFromList removes all instances of each given object from an array field.

For example, we can add items to the set-like “skills” field like so:

gameScore.AddRangeUniqueToList("skills", new[] { "flying", "kungfu" });
await gameScore.SaveAsync();

Note that it is not currently possible to atomically add and remove items from a list in the same save. You will have to call save in between every different kind of list operation.

Deleting Objects

To delete an object from the cloud:

await myObject.DeleteAsync();

You can delete a single field from an object with the Remove method:

// After this, the playerName field will be empty
myObject.Remove("playerName");

// Saves the field deletion to Parse Server
await myObject.SaveAsync();

Relational Data

Objects can have relationships with other objects. To model one-to-many relationships, any ParseObject can be used as a value in other ParseObjects. Internally, the Parse framework will store the referred-to object in just one place to maintain consistency.

For example, each Comment in a blogging app might correspond to one Post. To create a new Post with a single Comment, you could write:

// Create the post
var myPost = new ParseObject("Post")
{
    { "title", "I'm Hungry" },
    { "content", "Where should we go for lunch?" }
};

// Create the comment
var myComment = new ParseObject("Comment")
{
    { "content", "Let's do Sushirrito." }
};

// Add a relation between the Post and Comment
myComment["parent"] = myPost;

// This will save both myPost and myComment
await myComment.SaveAsync();

You can also link objects using just their ObjectIds like so:

myComment["parent"] = ParseObject.CreateWithoutData("Post", "1zEcyElZ80");

By default, when fetching an object, related ParseObjects are not fetched. These objects’ values cannot be retrieved until they have been fetched like so:

ParseObject post = fetchedComment.Get<ParseObject>("parent");
await post.FetchIfNeededAsync();

For a many-to-many relationship, use the ParseRelation object. This works similar to a List<ParseObject>, except that you don’t need to download all the objects in a relation at once. This allows ParseRelation to scale to many more objects than the List<ParseObject> approach. For example, a ParseUser may have many Posts that they might like. In this case, you can store the set of Posts that a ParseUser likes using GetRelation. In order to add a post to the list, the code would look something like:

var user = ParseUser.CurrentUser;
var relation = user.GetRelation<ParseObject>("likes");
relation.Add(post);
await user.SaveAsync();

You can remove a post from the ParseRelation with something like:

relation.Remove(post);

By default, the list of objects in this relation are not downloaded. You can get the list of Posts by using calling FindAsync on the ParseQuery returned by Query. The code would look like:

IEnumerable<ParseObject> relatedObjects = await relation.Query.FindAsync();

If you want only a subset of the Posts you can add extra constraints to the ParseQuery returned by Query like this:

var query = from post in relation.Query
            where post.CreatedAt > DateTime.Now - TimeSpan.FromDays(10)
                  // alternatively, add any other query constraints
            select post;
var relatedObjects = await query.FindAsync();

// or using LINQ
var query = relation.Query
    .WhereGreaterThan("createdAt", DateTime.Now - TimeSpan.FromDays(10));
    // alternatively, add any other query constraints
var relatedObjects = await query.FindAsync();

For more details on ParseQuery please look at the query portion of this guide. A ParseRelation behaves similar to a List<ParseObject>, so any queries you can do on lists of objects you can do on ParseRelations.

Subclasses

Parse is designed to get you up and running as quickly as possible. You can access all of your data using the ParseObject class and access any field with Get<T>(). In mature codebases, subclasses have many advantages, including terseness, extensibility, type-safety, and support for IntelliSense. Subclassing is completely optional, but can transform this code:

// Using dictionary-initialization syntax:
var shield = new ParseObject("Armor")
{
  { "displayName", "Wooden Shield" },
  { "fireproof", false },
  { "rupees", 50 }
};

// And later:
Console.WriteLine(shield.Get<string>("displayName"));
shield["fireproof"] = true;
shield["rupees"] = 500;

Into this:

// Using object-initialization syntax:
var shield = new Armor
{
  DisplayName = "Wooden Shield",
  IsFireproof = false,
  Rupees = 50
};

// And later:
Console.WriteLine(shield.DisplayName);
shield.IsFireproof = true;
shield.Rupees = 500;

Subclassing ParseObject

To create a ParseObject subclass:

1. Declare a subclass which extends ParseObject.
2. Add a ParseClassName attribute. Its value should be the string you would pass into the ParseObject constructor, and makes all future class name references unnecessary.
3. Ensure that your subclass has a public default (i.e. zero-argument) constructor. You must not modify any ParseObject fields in this constructor.
4. Call ParseObject.RegisterSubclass<YourClass>() in your code before calling ParseClient.Initialize(). The following code sucessfully implements and registers the Armor subclass of ParseObject:

// Armor.cs
using Parse;

[ParseClassName("Armor")]
public class Armor : ParseObject
{
}

// App.xaml.cs
using Parse;

public class App : Application
{
  public App()
  {
    ParseObject.RegisterSubclass<Armor>();
    ParseClient.Initialize(ParseApplicationId, ParseWindowsKey);
  }
}

Properties and Methods

Adding methods and properties to your ParseObject subclass helps encapsulate logic about the class. You can keep all your logic about a subject in one place rather than using separate classes for business logic and storage/transmission logic.

You can add properties for the fields of your ParseObject easily. Declare the getter and setter for the field as you normally would, but implement them in terms of GetProperty<T>() and SetProperty<T>(). Finally, add a ParseFieldName attribute to the property to fully integrate the property with Parse, enabling functionality like LINQ support and automatically raising INotifyPropertyChanged notifications. The following example creates a displayName field in the Armor class:

// Armor.cs
[ParseClassName("Armor")]
public class Armor : ParseObject
{
  [ParseFieldName("displayName")]
  public string DisplayName
  {
    get { return GetProperty<string>(); }
    set { SetProperty<string>(value); }
  }
}

You can now access the displayName field using armor.DisplayName and assign to it using armor.DisplayName = "Wooden Sword". This allows your IDE to provide autocompletion as you develop your app and allows typos to be caught at compile-time.

ParseRelation-typed properties can also be easily defined using GetRelationProperty<T>. For example:

// Armor.cs
[ParseClassName("Armor")]
public class Armor : ParseObject
{
  [ParseFieldName("attribute")]
  public ParseRelation<ArmorAttribute> Attributes
  {
    get { return GetRelationProperty<ArmorAttribute>(); }
  }
}

If you need more complicated logic than simple field access, you can declare your own methods as well:

public void TakeDamage(int amount) {
  // Decrease the armor's durability and determine whether it has broken
  this.Increment("durability", -amount);
  if (this.Durability < 0) {
    this.IsBroken = true;
  }
}

Initializing Subclasses

You should create new instances of your subclasses using the constructors you have defined. Your subclass must define a public default constructor that does not modify fields of the ParseObject, which will be used throughout the Parse SDK to create strongly-typed instances of your subclass.

To create a reference to an existing object, use ParseObject.CreateWithoutData<T>():

var armorReference = ParseObject.CreateWithoutData<Armor>(armor.ObjectId);

Queries on Subclasses

You can get a query for objects of a particular subclass using the generic ParseQuery<T> class. The following example queries for armors that the user can afford:

var query = from armor in new ParseQuery<Armor>()
            where armor.Rupees <= ((Player)ParseUser.CurrentUser).Rupees
            select armor;
IEnumerable<Armor> result = await query.FindAsync();

// or using LINQ
var query = new ParseQuery<Armor>()
    .WhereLessThanOrEqualTo("rupees", ((Player)ParseUser.CurrentUser).Rupees);
IEnumerable<Armor> result = await query.FindAsync();

Note that the ParseQuery LINQ provider understands properties with the ParseFieldName attribute, allowing you to use these strongly-typed properties fluently within your LINQ queries.

Queries

We’ve already seen how a ParseQuery with GetAsync can retrieve a single ParseObject from Parse. There are many other ways to retrieve data with ParseQuery - you can retrieve many objects at once, put conditions on the objects you wish to retrieve, and more.

Basic Queries

In many cases, GetAsync isn’t powerful enough to specify which objects you want to retrieve. The ParseQuery offers different ways to retrieve a list of objects rather than just a single object.

The general pattern is to create a ParseQuery, constraints to it, and then retrieve an IEnumerable of matching ParseObjectss using FindAsync. While ParseQuery supports a method-based approach for building your query, we highly recommend you use LINQ. This allows to use the full power of the LINQ C# and Visual Basic language features to create rich queries over your data.

For example, to retrieve scores with a particular playerName, use a “where” clause to constrain the value for a key.

var query = from gameScore in ParseObject.GetQuery("GameScore")
            where gameScore.Get<string>("playerName") == "Dan Stemkoski"
            select gameScore;
IEnumerable<ParseObject> results = await query.FindAsync();

// or using LINQ
var query = ParseObject.GetQuery("GameScore")
    .WhereEqualTo("playerName", "Dan Stemkoski");
IEnumerable<ParseObject> results = await query.FindAsync();

Query Constraints

There are several ways to put constraints on the objects found by a ParseQuery. You can filter out objects with a particular key-value pair with a LINQ where ... != ... clause or a call to WhereNotEqualTo:

var query = from gameScore in ParseObject.GetQuery("GameScore")
            where gameScore.Get<string>("playerName") != "Michael Yabuti"
            select gameScore;

// or using LINQ
var query = ParseObject.GetQuery("GameScore")
    .WhereNotEqualTo("playerName", "Michael Yabuti");

You can give multiple constraints, and objects will only be in the results if they match all of the constraints. In other words, it’s like an AND of constraints.

// The following queries are equivalent:
var query1 = from gameScore in ParseObject.GetQuery("GameScore")
             where !gameScore.Get<string>("playerName").Equals("Michael Yabuti")
             where gameScore.Get<int>("playerAge") > 18
             select gameScore;

var query2 = from gameScore in ParseObject.GetQuery("GameScore")
             where !gameScore.Get<string>("playerName").Equals("Michael Yabuti")
                 && gameScore.Get<int>("playerAge") > 18
             select gameScore;

// or using LINQ
var query = ParseObject.GetQuery("GameScore")
    .WhereNotEqualTo("playerName", "Michael Yabuti")
    .WhereGreaterThan("playerAge", 18);

You can limit the number of results by calling Limit. By default, results are limited to 100. In the old Parse hosted backend, the maximum limit was 1,000, but Parse Server removed that constraint:

query = query.Limit(10); // limit to at most 10 results

If you want exactly one result, a more convenient alternative may be to use FirstAsync or FirstOrDefaultAsync instead of using FindAsync.

var query = from gameScore in ParseObject.GetQuery("GameScore")
            where gameScore.Get<string>("playerEmail") == "[email protected]"
            select gameScore;
ParseObject obj = await query.FirstAsync();

// or using LINQ
var query = ParseObject.GetQuery("GameScore")
    .WhereEqualTo("playerEmail", "[email protected]");
ParseObject obj = await query.FirstAsync();

You can skip the first results by calling Skip. In the old Parse hosted backend, the maximum skip value was 10,000, but Parse Server removed that constraint. This can be useful for pagination:

query = query.Skip(10); // skip the first 10 results

For sortable types like numbers and strings, you can control the order in which results are returned:

// Sorts the results in ascending order by score and descending order by playerName
var query = from gameScore in ParseObject.GetQuery("GameScore")
            orderby gameScore.Get<int>("score") descending, gameScore.Get<string>("playerName")
            select gameScore;

// or using LINQ
// Sorts the results in ascending order by score and descending order by playerName
var query = ParseObject.GetQuery("GameScore")
    .OrderBy("score")
    .ThenByDescending("playerName");

For sortable types, you can also use comparisons in queries:

// Restricts to wins < 50
query = from gameScore in query
        where gameScore.Get<int>("wins") < 50
        select gameScore;

// Restricts to wins <= 50
query = from gameScore in query
        where gameScore.Get<int>("wins") <= 50
        select gameScore;

// Restricts to wins > 50
query = from gameScore in query
        where gameScore.Get<int>("wins") > 50
        select gameScore;

// Restricts to wins >= 50
query = from gameScore in query
        where gameScore.Get<int>("wins") >= 50
        select gameScore;

// or using LINQ
// Restricts to wins < 50
query = query.WhereLessThan("wins", 50);

// Restricts to wins <= 50
query = query.WhereLessThanOrEqualTo("wins", 50);

// Restricts to wins > 50
query = query.WhereGreaterThan("wins", 50);

// Restricts to wins >= 50
query = query.WhereGreaterThanOrEqualTo("wins", 50);

If you want to retrieve objects matching several different values, you can use WhereContainedIn or a Contains LINQ query, providing an list of acceptable values. This is often useful to replace multiple queries with a single query. For example, if you want to retrieve scores made by any player in a particular list:

// Finds scores from any of Jonathan, Dario, or Shawn
var names = new[] { "Jonathan Walsh", "Dario Wunsch", "Shawn Simon" };
var query = from gameScore in ParseObject.GetQuery("GameScore")
            where names.Contains(gameScore.Get<string>("playerName"))
            select gameScore;

// or using LINQ
// Finds scores from any of Jonathan, Dario, or Shawn
var names = new[] { "Jonathan Walsh", "Dario Wunsch", "Shawn Simon" };
var query = ParseObject.GetQuery("GameScore")
    .WhereContainedIn("playerName", names);

If you want to retrieve objects that do not match any of several values you can use WhereNotContainedIn or a !Contains LINQ query, providing an list of acceptable values. For example, if you want to retrieve scores from players besides those in a list:

// Finds scores from any of Jonathan, Dario, or Shawn
var names = new[] { "Jonathan Walsh", "Dario Wunsch", "Shawn Simon" };
var query = from gameScore in ParseObject.GetQuery("GameScore")
            where !names.Contains(gameScore.Get<string>("playerName"))
            select gameScore;

// or using LINQ
// Finds scores from any of Jonathan, Dario, or Shawn
var names = new[] { "Jonathan Walsh", "Dario Wunsch", "Shawn Simon" };
var query = ParseObject.GetQuery("GameScore")
    .WhereNotContainedIn("playerName", names);

If you want to retrieve objects that have a particular key set, you can use WhereExists or an ContainsKey LINQ query. Conversely, if you want to retrieve objects without a particular key set, you can use WhereDoesNotExist or an !ContainsKey LINQ query.

// Finds objects that have the score set
var query = from gameScore in ParseObject.GetQuery("GameScore")
            where gameScore.ContainsKey("score")
            select gameScore;

// Finds objects that don't have the score set
var query = from gameScore in ParseObject.GetQuery("GameScore")
            where !gameScore[.ContainsKey("score")
            select gameScore;

// or using LINQ
// Finds objects that have the score set
var query = ParseObject.GetQuery("GameScore")
    .WhereExists("score");

// Finds objects that don't have the score set
var query = ParseObject.GetQuery("GameScore")
    .WhereDoesNotExist("score");

You can use the WhereMatchesKeyInQuery method or a join LINQ query to get objects where a key matches the value of a key in a set of objects resulting from another query. For example, if you have a class containing sports teams and you store a user’s hometown in the user class, you can issue one query to find the list of users whose hometown teams have winning records. The query would look like:

var teamQuery = from team in ParseObject.GetQuery("Team")
                where team.Get<double>("winPct") > 0.5
                select team;
var userQuery = from user in ParseUser.Query
                join team in teamQuery on user["hometown"] equals team["city"]
                select user;
IEnumerable<ParseUser> results = await userQuery.FindAsync();
// results will contain users with a hometown team with a winning record

// or using LINQ
var teamQuery = ParseQuery.GetQuery("Team")
    .WhereGreaterThan("winPct", 0.5);
var userQuery = ParseUser.Query
    .WhereMatchesKeyInQuery("hometown", "city", teamQuery);
IEnumerable<ParseUser> results = await userQuery.FindAsync();
// results will contain users with a hometown team with a winning record

Queries on List Values

For keys with an array type, you can find objects where the key’s array value contains 2 by:

// Find objects where the list in listKey contains 2.
var query = from obj in ParseObject.GetQuery("MyClass")
            where obj.Get<IList<int>>("listKey").Contains(2)
            select obj;

// or using LINQ
// Find objects where the list in listKey contains 2.
var query = ParseObject.GetQuery("MyClass")
    .WhereEqualTo("listKey", 2);

Queries on String Values

Use WhereStartsWith or a StartsWith LINQ query to restrict to string values that start with a particular string. Similar to a MySQL LIKE operator, this is indexed so it is efficient for large datasets:

// Finds barbecue sauces that start with "Big Daddy's".
var query = from sauce in ParseObject.GetQuery("BarbecueSauce")
            where sauce.Get<string>("name").StartsWith("Big Daddy's")
            select sauce;

// or using LINQ
// Finds barbecue sauces that start with "Big Daddy's".
var query = ParseObject.GetQuery("BarbecueSauce")
    .WhereStartsWith("name", "Big Daddy's");

The above example will match any BarbecueSauce objects where the value in the “name” String key starts with “Big Daddy’s”. For example, both “Big Daddy’s” and “Big Daddy’s BBQ” will match, but “big daddy’s” or “BBQ Sauce: Big Daddy’s” will not.

Queries that have regular expression constraints are very expensive. Refer to the Performance Guide for more details.

Relational Queries

There are several ways to issue queries for relational data. If you want to retrieve objects where a field matches a particular ParseObject, you can use WhereEqualTo or a == LINQ query just like for other data types. For example, if each Comment has a Post object in its post field, you can fetch comments for a particular Post:

// Assume ParseObject myPost was previously created.
var query = from comment in ParseObject.GetQuery("Comment")
            where comment["post"] == myPost
            select comment;

var comments = await query.FindAsync();
// comments now contains the comments for myPost

// or using LINQ
// Assume ParseObject myPost was previously created.
var query = ParseObject.GetQuery("Comment")
    .WhereEqualTo("post", myPost);

var comments = await query.FindAsync();
//comments now contains the comments for myPost

You can also do relational queries by ObjectId:

var query = from comment in ParseObject.GetQuery("Comment")
            where comment["post"] == ParseObject.CreateWithoutData("Post", "1zEcyElZ80")
            select comment;

// or using LINQ
var query = ParseObject.GetQuery("Comment")
    .WhereEqualTo("post", ParseObject.CreateWithoutData("Post", "1zEcyElZ80"));

If you want to retrieve objects where a field contains a ParseObject that matches a different query, you can use WhereMatchesQuery or a join LINQ query. In order to find comments for posts with images, you can do:

var imagePosts = from post in ParseObject.GetQuery("Post")
                 where post.ContainsKey("image")
                 select post;
var query = from comment in ParseObject.GetQuery("Comment")
            join post in imagePosts on comment["post"] equals post
            select comment;

var comments = await query.FindAsync();
// comments now contains the comments for posts with images

// or using LINQ
var imagePosts = ParseObject.GetQuery("Post")
    .WhereExists("image");
var query = ParseObject.GetQuery("Comment")
    .WhereMatchesQuery("post", imagePosts);

var comments = await query.FindAsync();
// comments now contains the comments for posts with images

If you want to retrieve objects where a field contains a ParseObject that does not match a different query, you can use WhereDoesNotMatchQuery. In order to find comments for posts without images, you can do:

var imagePosts = from post in ParseObject.GetQuery("Post")
                 where post.ContainsKey("image")
                 select post;
var query = ParseObject.GetQuery("Comment")
    .WhereDoesNotMatchQuery("post", imagePosts);

var comments = await query.FindAsync();
// comments now contains the comments for posts without images

// or using LINQ
var imagePosts = ParseObject.GetQuery("Post")
    .WhereExists("image");
var query = ParseObject.GetQuery("Comment")
    .WhereDoesNotMatchQuery("post", imagePosts);

var comments = await query.FindAsync();
// comments now contains the comments for posts without images

In some situations, you want to return multiple types of related objects in one query. You can do this with the Include method. For example, let’s say you are retrieving the last ten comments, and you want to retrieve their related posts at the same time:

// Retrieve the most recent comments
var query = from comment in ParseObject.GetQuery("Comment")
                                       // Only retrieve the last 10 comments
                                       .Limit(10)
                                       // Include the post data with each comment
                                       .Include("post")
            orderby comment.CreatedAt descending
            select comment;

var comments = await comments.FindAsync();

// Comments now contains the last ten comments, and the "post" field
// contains an object that has already been fetched.  For example:
foreach (var comment in comments)
{
    // This does not require a network access.
    var post = comment.Get<ParseObject>("post");
    Debug.WriteLine("Post title: " + post["title"]);
}

// or using LINQ
// Retrieve the most recent comments
var query = ParseObject.GetQuery("Comment")
    .OrderByDescending("createdAt")
    .Limit(10) // Only retrieve the last 10 comments
    .Include("post"); // Include the post data with each comment

// Only retrieve the last 10 comments
query = query.Limit(10);

// Include the post data with each comment
query = query.Include("post");

var comments = await comments.FindAsync();

// Comments now contains the last ten comments, and the "post" field
// contains an object that has already been fetched.  For example:
foreach (var comment in comments)
{
    // This does not require a network access.
    var post = comment.Get<ParseObject>("post");
    Debug.WriteLine("Post title: " + post["title"]);
}

You can also do multi level includes using dot notation. If you wanted to include the post for a comment and the post’s author as well you can do:

query = query.Include("post.author");

You can issue a query with multiple fields included by calling Include multiple times. This functionality also works with ParseQuery helpers like FirstAsync and GetAsync

Counting Objects

Note: In the old Parse hosted backend, count queries were rate limited to a maximum of 160 requests per minute. They also returned inaccurate results for classes with more than 1,000 objects. But, Parse Server has removed both constraints and can count objects well above 1,000.

If you just need to count how many objects match a query, but you do not need to retrieve the objects that match, you can use CountAsync instead of FindAsync. For example, to count how many games have been played by a particular player:

var query = from gameScore in ParseObject.GetQuery("GameScore")
            where gameScore["playerName"] == "Sean Plott"
            select gameScore;
var count = await query.CountAsync();

// or using LINQ
// First set up a callback.
var query = ParseObject.GetQuery("GameScore")
    .WhereEqualTo("playerName", "Sean Plott");
var count = await query.CountAsync();

Compound Queries

If you want to find objects that match one of several queries, you can use the Or method. For instance, if you want to find players with either have a lot of wins or a few wins, you can do:

var lotsOfWins = from player in ParseObject.GetQuery("Player")
                 where player.Get<int>("wins") > 150
                 select player;

var fewWins = from player in ParseObject.GetQuery("Player")
              where player.Get<int>("wins") < 5
              select player;

ParseQuery<ParseObject> query = lotsOfWins.Or(fewWins);

var results = await query.FindAsync();
// results contains players with lots of wins or only a few wins.

// or using LINQ
var lotsOfWins = ParseObject.GetQuery("Player")
    .WhereGreaterThan("wins", 150);

var fewWins = ParseObject.GetQuery("Player")
    .WhereLessThan("wins", 5);

ParseQuery<ParseObject> query = lotsOfWins.Or(fewWins);
// results contains players with lots of wins or only a few wins.

You can add additional constraints to the newly created ParseQuery that act as an ‘and’ operator.

Note that we do not, however, support GeoPoint or non-filtering constraints (e.g. Near, WhereWithinGeoBox, Limit, Skip, OrderBy..., Include) in the subqueries of the compound query.

Users

At the core of many apps, there is a notion of user accounts that lets users access their information in a secure manner. We provide a specialized user class called ParseUser that automatically handles much of the functionality required for user account management.

With this class, you’ll be able to add user account functionality in your app.

ParseUser is a subclass of ParseObject and has all the same features, such as flexible schema, automatic persistence, and a key value interface. All the methods that are on ParseObject also exist in ParseUser. The difference is that ParseUser has some special additions specific to user accounts.

ParseUser Properties

ParseUser has several properties that set it apart from ParseObject:

• Username: The username for the user (required).
• Password: The password for the user (required on signup).
• Email: The email address for the user (optional).

We’ll go through each of these in detail as we run through the various use cases for users. Keep in mind that if you set Username and Email through these properties, you do not need to set it using the indexer on ParseObject — this is set for you automatically.

Signing Up

The first thing your app will do is probably ask the user to sign up. The following code illustrates a typical sign up:

public async void SignUpButton_Click(object sender, RoutedEventArgs e)
{
    var user = new ParseUser()
    {
        Username = "my name",
        Password = "my pass",
        Email = "[email protected]"
    };

    // other fields can be set just like with ParseObject
    user["phone"] = "415-392-0202";

    await user.SignUpAsync();
}

This call will asynchronously create a new user in your Parse App. Before it does this, it also checks to make sure that both the username and email are unique. Also, it securely hashes the password in the cloud using bcrypt. We never store passwords in plaintext, nor will we ever transmit passwords back to the client in plaintext.

Note that we used the SignUpAsync method, not the SaveAsync method. New ParseUsers should always be created using the SignUpAsync method. Subsequent updates to a user can be done by calling SaveAsync.

If a signup isn’t successful, you should catch the exception thrown by the SignUpAsync. The most likely case is that the username or email has already been taken by another user. You should clearly communicate this to your users, and ask them try a different username.

You are free to use an email address as the username. Simply ask your users to enter their email, but fill it in both the Username and Email properties — ParseObject will work as normal. We’ll go over how this is handled in the reset password section.

Logging In

Of course, after you allow users to sign up, you need to let them log in to their account in the future. To do this, you can use the class method LogInAsync.

try
{
    await ParseUser.LogInAsync("myname", "mypass");
    // Login was successful.
}
catch (Exception e)
{
    // The login failed. Check the error to see why.
}

Verifying Emails

Enabling email verification in an application’s settings allows the application to reserve part of its experience for users with confirmed email addresses. Email verification adds the emailVerified key to the ParseUser object. When a ParseUser’s Email is set or modified, emailVerified is set to false. Parse then emails the user a link which will set emailVerified to true.

There are three emailVerified states to consider:

1. true - the user confirmed his or her email address by clicking on the link Parse emailed them. ParseUsers can never have a true value when the user account is first created.
2. false - at the time the ParseUser object was last refreshed, the user had not confirmed his or her email address. If emailVerified is false, consider calling FetchAsync on the ParseUser.
3. missing - the ParseUser was created when email verification was off or the ParseUser does not have an email.

Current User

It would be bothersome if the user had to log in every time they open your app. You can avoid this by using the cached ParseUser.CurrentUser object.

Whenever you use any signup or login methods, the user is cached on disk. You can treat this cache as a session, and automatically assume the user is logged in:

if (ParseUser.CurrentUser != null)
{
    // do stuff with the user
}
else
{
    // show the signup or login screen
}

You can clear the current user by logging them out:

ParseUser.LogOut();
var currentUser = ParseUser.CurrentUser; // this will now be null

Setting the Current User

If you’ve created your own authentication routines, or otherwise logged in a user on the server side, you can now pass the session token to the client and use the become method. This method will ensure the session token is valid before setting the current user.

try
{
  await ParseUser.becomeAsync("session-token-here");
  // The current user is now set to user.
}
catch (Exception e)
{
  // The token could not be validated.
}

Security For User Objects

The ParseUser class is secured by default. Data stored in a ParseUser can only be modified by that user. By default, the data can still be read by any client. Thus, some ParseUser objects are authenticated and can be modified, whereas others are read-only.

Specifically, you are not able to invoke the SaveAsync or DeleteAsync methods unless the ParseUser was obtained using an authenticated method, like LogInAsync or SignUpAsync. This ensures that only the user can alter their own data.

The following illustrates this security policy:

var user = await ParseUser.LogInAsync("my_username", "my_password");
user.Username = "my_new_username"; // attempt to change username
await user.SaveAsync(); // This succeeds, since this user was
                        // authenticated on the device

ParseUser.LogOut();
// Get the user from a non-authenticated method
user = await ParseUser.Query.GetAsync(user.ObjectId);
user.Username = "another_username";

// This will throw an exception, since the ParseUser is not authenticated
await user.SaveAsync();

The ParseUser obtained from Current will always be authenticated.

If you need to check if a ParseUser is authenticated, you can check the IsAuthenticated property. You do not need to check IsAuthenticated with ParseUser objects that are obtained via an authenticated method.

Security For Other Objects

The same security model that applies to the ParseUser can be applied to other objects. For any object, you can specify which users are allowed to read the object, and which users are allowed to modify an object. To support this type of security, each object has an access control list, implemented by the ParseACL class.

The simplest way to use a ParseACL is to specify that an object may only be read or written by a single user. To create such an object, there must first be a logged in ParseUser. Then, the ParseACL constructor generates a ParseACL that limits access to that user. An object’s ACL is updated when the object is saved, like any other property. Thus, to create a private note that can only be accessed by the current user:

var privateNote = new ParseObject("Note");
privateNote["content"] = "This note is private!";
privateNote.ACL = new ParseACL(ParseUser.CurrentUser);
await privateNote.SaveAsync();

This note will then only be accessible to the current user, although it will be accessible to any device where that user is signed in. This functionality is useful for applications where you want to enable access to user data across multiple devices, like a personal todo list.

Permissions can also be granted on a per-user basis. You can add permissions individually to a ParseACL using SetReadAccess and SetWriteAccess. For example, let’s say you have a message that will be sent to a group of several users, where each of them have the rights to read and delete that message:

var groupMessage = new ParseObject("Message");
var groupACL = new ParseACL();

// userList is an IEnumerable<ParseUser> with the users we are sending
// this message to.
foreach (var user in userList)
{
    groupACL.SetReadAccess(user, true);
    groupACL.SetWriteAccess(user, true);
}

groupMessage.ACL = groupACL;
await groupMessage.SaveAsync();

You can also grant permissions to all users at once using the PublicReadAccess and PublicWriteAccess properties. This allows patterns like posting comments on a message board. For example, to create a post that can only be edited by its author, but can be read by anyone:

var publicPost = new ParseObject("Post");
var postACL = new ParseACL(ParseUser.CurrentUser)
{
    PublicReadAccess = true,
    PublicWriteAccess = false
};
publicPost.ACL = postACL;
await publicPost.SaveAsync();

Operations that are forbidden, such as deleting an object that you do not have write access to, result in a ParseException with a ObjectNotFound error code. For security purposes, this prevents clients from distinguishing which object ids exist but are secured, versus which object ids do not exist at all.

Resetting Passwords

As soon as you introduce passwords into a system, users will forget them. In such cases, our library provides a way to let them securely reset their password.

To kick off the password reset flow, ask the user for their email address, and call:

await ParseUser.RequestPasswordResetAsync("[email protected]");

This will attempt to match the given email with the user’s email or username field, and will send them a password reset email. By doing this, you can opt to have users use their email as their username, or you can collect it separately and store it in the email field.

The flow for password reset is as follows:

1. User requests that their password be reset by typing in their email.
2. Parse sends an email to their address, with a special password reset link.
3. User clicks on the reset link, and is directed to a special Parse page that will allow them type in a new password.
4. User types in a new password. Their password has now been reset to a value they specify.

Note that the messaging in this flow will reference your app by the name that you specified when you created this app on Parse.

Querying

To query for users, you need to use the special user query:

var women = await (from user in ParseUser.Query
                   where user.Get<string>("gender") == "female"
                   select user).FindAsync();

// or using LINQ
var women = await ParseUser.Query
    .WhereEqualTo("gender", "female")
    .FindAsync();

In addition, you can use GetAsync to get a ParseUser by id.

Associations

Associations involving a ParseUser work right out of the box. For example, let’s say you’re making a blogging app. To store a new post for a user and retrieve all their posts:

// Make a new post
var post = new ParseObject("Post")
{
    { "title", "My New Post" },
    { "body", "This is some great content." },
    { "user", ParseUser.CurrentUser }
};
await post.SaveAsync();

// Find all posts by the current user
var usersPosts = await (from post in ParseObject.GetQuery("Post")
                        where post.Get<ParseUser>("user") == ParseUser.CurrentUser
                        select post).FindAsync();

// or using LINQ
// Make a new post
var post = new ParseObject("Post")
{
    { "title", "My New Post" },
    { "body", "This is some great content." },
    { "user", ParseUser.CurrentUser }
};
await post.SaveAsync();

// Find all posts by the current user
var usersPosts = await ParseObject.GetQuery("Post")
    .WhereEqualTo("user", ParseUser.CurrentUser)
    .FindAsync();

Facebook Users

Parse provides an easy way to integrate Facebook with your application. The ParseFacebookUtils class integrates with ParseUser to make linking your users to their Facebook identities easy.

Using our Facebook integration, you can associate an authenticated Facebook user with a ParseUser. With just a few lines of code, you’ll be able to provide a “log in with Facebook” option in your app, and be able to save their data to Parse.

Setting up Facebook

To start using Facebook with Parse, you need to:

1. Set up a Facebook app, if you haven’t already. In the “Advanced” tab of your app’s settings page, Make sure that your app’s “App Type” (in the “Authentication” section) is set to “Native/Desktop”.
2. Add your application’s Facebook Application ID on your Parse application’s settings page.
3. In your Application constructor, call ParseFacebookUtils.Initialize() with your Facebook App ID:

public App()
{
    // App.xaml initialization
    ParseClient.Initialize("Your Application ID", "Your .NET Key");
    ParseFacebookUtils.Initialize("Your Facebook App Id");
    // Other initialization
}

There are two main ways to use Facebook with your Parse users: (1) logging in as a Facebook user and creating a ParseUser, or (2) linking Facebook to an existing ParseUser.

Login & Signup

ParseFacebookUtils provides a way to allow your ParseUsers to log in or sign up through Facebook. This is accomplished using the LogInAsync() method. To display Facebook’s web browser OAuth flow to your users, you’ll need to pass LogInAsync a web browser control (which you’ll usually define in XAML) and dismiss it when you’ve completed login:

// Make your browser control visible
ParseUser user = await ParseFacebookUtils.LogInAsync(browser, null);
// Hide your browser control

When this code is run, the following happens:

1. The user is shown the Facebook login dialog.
2. The user authenticates via Facebook, and your app receives a callback.
3. Our SDK receives the user’s Facebook access data and saves it to a ParseUser. If no ParseUser exists with the same Facebook ID, then a new ParseUser is created.
4. The awaited Task completes and your code continues executing.
5. The current user reference will be updated to this user.

You may optionally provide a list of strings that specifies what permissions your app requires from the Facebook user. For example:

// Make your browser control visible
try
{
    ParseUser user = await ParseFacebookUtils.LogInAsync(
        browser, new[] { "user_likes", "email" });
    // The user logged in with Facebook!
}
catch
{
    // User cancelled the Facebook login or did not fully authorize.
}
// Hide your browser control

ParseUser integration doesn’t require any permissions to work out of the box (ie. null or specifying no permissions is perfectly acceptable). Read more about permissions on Facebook’s developer guide.

Linking

If you want to associate an existing ParseUser with a Facebook account, you can link it like so:

if (!ParseFacebookUtils.IsLinked(user))
{
    // Make your browser control visible
    try
    {
        await ParseFacebookUtils.LinkAsync(user, browser, null);
        // The user logged in with Facebook!
    }
    catch
    {
        // User cancelled the Facebook login or did not fully authorize.
    }
    // Hide your browser control
}

The steps that happen when linking are very similar to log in. The difference is that on successful login, the existing ParseUser is updated with the Facebook information. Future logins via Facebook will now log the user into their existing account.

If you want to unlink a Facebook account from a user, simply do this:

await ParseFacebookUtils.UnlinkAsync(user);

Single Sign-on for Windows 8

WinRT lets you implement single sign-on with Facebook using its [WebAuthenticationBroker](http://msdn.microsoft.com/library/windows/apps/br227025) API. This allows users to log into Facebook once and then share that login across all of their apps, so they don’t have to re-enter their username and password for every app.

Parse supports single sign-on with Facebook using this mechanism. Adding it to your app requires just two steps:

• Add your app’s Package Security Identifier to your Facebook App settings page under “Windows Store ID”. You can easily get this ID by calling:

WebAuthenticationBroker.GetCurrentApplicationCallbackUri().AbsoluteUri

The identifier is everything after `"ms-app://"`.

• Instead of showing and hiding a browser control as described above, use the simpler ParseFacebookUtils APIs that take only a list of permissions:

// Log into Facebook using Single Sign-on
ParseUser user = await ParseFacebookUtils.LogInAsync(permissions);

    // Link the current user to Facebook using Single Sign-on
await ParseFacebookUtils.LinkAsync(ParseUser.CurrentUser, permissions);

Single Sign-on for Windows Phone

The Facebook app for Windows Phone makes signing into apps with Facebook easy for users by providing a mechanism for single sign-on. Once a user has signed into the Facebook app on their device, when they sign into apps that use Facebook login, they will not need to re-enter their email address and password for each app. This works by temporarily navigating to the Facebook app in order to provide authorization for the app logging in.

Parse supports single sign-on using this mechanism. To add support to your app:

• You will need to locate your app’s product ID. During development, you can find this in your app’s WMAppManifest.xml. When you submit your app to the store for the first time, your app will be assigned a new product ID, which you’ll need to add to your app as described below. Whenever you use your product ID while following this guide, you should remove any of the following characters: '-', '{', '}'.

• You will need to configure your WMAppManifest.xml file as described here to have your app handle URIs with the following protocol:

<Protocol Name="msft-{ProductId}"
          NavUriFragment="encodedLaunchUri=%s"
          TaskID="_default" />

• Add your product ID to your Facebook app settings page under “Windows Phone Store ID”.

• Add the following code to your application’s App.xaml.cs in the InitializePhoneApplication() method:

RootFrame.Navigating += async (sender, e) =>
{
    if (ParseFacebookUtils.IsLogInRedirect(e.Uri))
    {
        // This code is called when the Facebook app returns control to your app.
        // You must provide a landing page URI, which ParseFacebookUtils will
        // navigate to as it waits for the user to be created or logged into
        // your Parse app.
        var user = await ParseFacebookUtils.EndLogInAsync(sender,
            e, new Uri("/LandingPage.xaml", UriKind.Relative));

            // If you await the return value of this method, you can begin using the
        // new user once it becomes available or catch any errors.
    }
};

• To initiate Facebook a Facebook login (and switch to the Facebook app), add the following code:

ParseFacebookUtils.BeginLogin(permissions);

Facebook SDK and Parse

Microsoft provides an open-source SDK for making Graph API requests to Facebook. The SDK is available on NuGet, and you can learn more about it from their website.

To use the Facebook SDK to fetch information about the current user, for example, you would install it using NuGet and then write code similar to this:

var fb = new FacebookClient();
fb.AccessToken = ParseFacebookUtils.AccessToken;
var me = await fb.GetTaskAsync("me");

With the AccessToken provided by ParseFacebookUtils, you should be able to use your choice of 3rd party Facebook SDKs to interact with Facebook on behalf of your user.

Sessions

Sessions represent an instance of a user logged into a device. Sessions are automatically created when users log in or sign up. They are automatically deleted when users log out. There is one distinct Session object for each user-installation pair; if a user issues a login request from a device they’re already logged into, that user’s previous Session object for that Installation is automatically deleted. Session objects are stored on Parse in the Session class, and you can view them on the Parse Dashboard Data Browser. We provide a set of APIs to manage Session objects in your app.

Session is a subclass of a Parse Object, so you can query, update, and delete sessions in the same way that you manipulate normal objects on Parse. Because Parse Server automatically creates sessions when you log in or sign up users, you should not manually create Session objects unless you are building an IoT app (e.g. Arduino or Embedded C). Deleting a Session will log the user out of the device that is currently using this session’s token.

Unlike other Parse objects, the Session class does not have Cloud Code triggers. So you cannot register a beforeSave or afterSave handler for the Session class.

Session Properties

The Session object has these special fields:

• sessionToken (readonly): String token for authentication on Parse API requests. In the response of Session queries, only your current Session object will contain a session token.
• user: (readonly) Pointer to the User object that this session is for.
• createdWith (readonly): Information about how this session was created (e.g. { "action": "login", "authProvider": "password"}).
  • action could have values: login, signup, create, or upgrade. The create action is when the developer manually creates the session by saving a Session object. The upgrade action is when the user is upgraded to revocable session from a legacy session token.
  • authProvider could have values: password, anonymous, facebook, or twitter.
• expiresAt (readonly): Approximate UTC date when this Session object will be automatically deleted. You can configure session expiration settings (either 1-year inactivity expiration or no expiration) in your app’s Parse Dashboard settings page.
• installationId (can be set only once): String referring to the Installation where the session is logged in from. For Parse SDKs, this field will be automatically set when users log in or sign up. All special fields except installationId can only be set automatically by Parse Server. You can add custom fields onto Session objects, but please keep in mind that any logged-in device (with session token) can read other sessions that belong to the same user (unless you disable Class-Level Permissions, see below).

Handling Invalid Session Token Error

With revocable sessions, your current session token could become invalid if its corresponding Session object is deleted from your Parse Server. This could happen if you implement a Session Manager UI that lets users log out of other devices, or if you manually delete the session via Cloud Code, REST API, or Data Browser. Sessions could also be deleted due to automatic expiration (if configured in app settings). When a device’s session token no longer corresponds to a Session object on your Parse Server, all API requests from that device will fail with “Error 209: invalid session token”.

To handle this error, we recommend writing a global utility function that is called by all of your Parse request error callbacks. You can then handle the “invalid session token” error in this global function. You should prompt the user to login again so that they can obtain a new session token. This code could look like this:

public class ParseErrorHandler {
  public static void HandleParseError(ParseException e) {
    switch (e.Code) {
      case ParseException.ErrorCode.InvalidSessionToken:
        HandleInvalidSessionToken()
        break;

      ... // Other Parse API errors that you want to explicitly handle
    }
  }

  private static void HandleInvalidSessionToken() {
    //--------------------------------------
    // Option 1: Show a message asking the user to log out and log back in.
    //--------------------------------------
    // If the user needs to finish what they were doing, they have the opportunity to do so.

    //--------------------------------------
    // Option #2: Show login screen so user can re-authenticate.
    //--------------------------------------
    // You may want this if the logout button is inaccessible in the UI.
  }
});

// In all API requests, call the global error handler, e.g.
query.FindAsync().ContinueWith(t => {
  if (t.IsFaulted) {
    // Query Failed - handle an error.
    ParseErrorHandler.HandleParseError(t.Exception.InnerException as ParseException);
  } else {
    // Query Succeeded - continue your app logic here.
  }
});

Session Security

Session objects can only be accessed by the user specified in the user field. All Session objects have an ACL that is read and write by that user only. You cannot change this ACL. This means querying for sessions will only return objects that match the current logged-in user.

When you log in a user via a User login method, Parse will automatically create a new unrestricted Session object in your Parse Server. Same for signups and Facebook/Twitter logins.

You can configure Class-Level Permissions (CLPs) for the Session class just like other classes on Parse. CLPs restrict reading/writing of sessions via the Session API, but do not restrict Parse Server’s automatic session creation/deletion when users log in, sign up, and log out. We recommend that you disable all CLPs not needed by your app. Here are some common use cases for Session CLPs:

• Find, Delete — Useful for building a UI screen that allows users to see their active session on all devices, and log out of sessions on other devices. If your app does not have this feature, you should disable these permissions.
• Create — Useful for apps that provision user sessions for other devices from the phone app. You should disable this permission when building apps for mobile and web. For IoT apps, you should check whether your IoT device actually needs to access user-specific data. If not, then your IoT device does not need a user session, and you should disable this permission.
• Get, Update, Add Field — Unless you need these operations, you should disable these permissions.

Roles

As your app grows in scope and user-base, you may find yourself needing more coarse-grained control over access to pieces of your data than user-linked ACLs can provide. To address this requirement, Parse supports a form of Role-based Access Control. Roles provide a logical way of grouping users with common access privileges to your Parse data. Roles are named objects that contain users and other roles. Any permission granted to a role is implicitly granted to its users as well as to the users of any roles that it contains.

For example, in your application with curated content, you may have a number of users that are considered “Moderators” and can modify and delete content created by other users. You may also have a set of users that are “Administrators” and are allowed all of the same privileges as Moderators, but can also modify the global settings for the application. By adding users to these roles, you can ensure that new users can be made moderators or administrators, without having to manually grant permission to every resource for each user.

We provide a specialized class called ParseRole that represents these role objects in your client code. ParseRole is a subclass of ParseObject, and has all of the same features, such as a flexible schema, automatic persistence, and a key value interface. All the methods that are on ParseObject also exist on ParseRole. The difference is that ParseRole has some additions specific to management of roles.

ParseRole Properties

ParseRole has several properties that set it apart from ParseObject:

• name: The name for the role. This value is required, must be unique, and can only be set once as a role is being created. The name must consist of alphanumeric characters, spaces, -, or _. This name will be used to identify the Role without needing its objectId.
• users: A relation to the set of users that will inherit permissions granted to the containing role.
• roles: A relation to the set of roles whose users and roles will inherit permissions granted to the containing role.

Security for Role Objects

The ParseRole uses the same security scheme (ACLs) as all other objects on Parse, except that it requires an ACL to be set explicitly. Generally, only users with greatly elevated privileges (e.g. a master user or Administrator) should be able to create or modify a Role, so you should define its ACLs accordingly. Remember, if you give write-access to a ParseRole to a user, that user can add other users to the role, or even delete the role altogether.

To create a new ParseRole, you would write:

// By specifying no write privileges for the ACL, we can ensure the role cannot be altered.
var roleACL = new ParseACL()
roleACL.PublicReadAccess = true;
var role = new ParseRole("Administrator", roleACL);
await role.SaveAsync();

You can add users and roles that should inherit your new role’s permissions through the “users” and “roles” relations on ParseRole:

var role = new ParseRole(roleName, roleACL);
foreach (ParseUser user in usersToAddToRole)
{
    role.Users.Add(user);
}
foreach (ParseRole childRole in rolesToAddToRole)
{
    role.Roles.Add(childRole);
}
await role.SaveAsync();

Take great care when assigning ACLs to your roles so that they can only be modified by those who should have permissions to modify them.

Role Based Security for Other Objects

Now that you have created a set of roles for use in your application, you can use them with ACLs to define the privileges that their users will receive. Each ParseObject can specify a ParseACL, which provides an access control list that indicates which users and roles should be granted read or write access to the object.

Giving a role read or write permission to an object is straightforward. You can either use the ParseRole:

var moderators = await (from role in ParseRole.Query
                        where role.Name == "Moderators"
                        select role).FirstAsync();
var wallPost = new ParseObject("WallPost");
var postACL = new ParseACL();
postACL.SetRoleWriteAccess(moderators, true);
wallPost.ACL = postACL;
await wallPost.SaveAsync();

You can avoid querying for a role by specifying its name for the ACL:

var wallPost = new ParseObject("WallPost");
var postACL = new ParseACL();
postACL.SetRoleWriteAccess("Moderators", true);
wallPost.ACL = postACL;
await wallPost.SaveAsync();

Role Hierarchy

As described above, one role can contain another, establishing a parent-child relationship between the two roles. The consequence of this relationship is that any permission granted to the parent role is implicitly granted to all of its child roles.

These types of relationships are commonly found in applications with user-managed content, such as forums. Some small subset of users are “Administrators”, with the highest level of access to tweaking the application’s settings, creating new forums, setting global messages, and so on. Another set of users are “Moderators”, who are responsible for ensuring that the content created by users remains appropriate. Any user with Administrator privileges should also be granted the permissions of any Moderator. To establish this relationship, you would make your “Administrators” role a child role of “Moderators”, like this:

ParseRole administrators = /* Your "Administrators" role */;
ParseRole moderators = /* Your "Moderators" role */;
moderators.Roles.Add(administrators);
await moderators.SaveAsync();

Files

The ParseFile

ParseFile lets you store application files in the cloud that would otherwise be too large or cumbersome to fit into a regular ParseObject. The most common use case is storing images but you can also use it for documents, videos, music, and any other binary data.

Getting started with ParseFile is easy. First, you’ll need to have the data in byte[] or Stream form and then create a ParseFile with it. In this example, we’ll just use a string:

byte[] data = System.Text.Encoding.UTF8.GetBytes("Working at Parse is great!");
ParseFile file = new ParseFile("resume.txt", data);

Notice in this example that we give the file a name of resume.txt. There’s two things to note here:

• You don’t need to worry about filename collisions. Each upload gets a unique identifier so there’s no problem with uploading multiple files named resume.txt.
• It’s important that you give a name to the file that has a file extension. This lets Parse figure out the file type and handle it accordingly. So, if you’re storing PNG images, make sure your filename ends with .png.

Next you’ll want to save the file up to the cloud. As with ParseObject, you can call SaveAsync to save the file to Parse.

await file.SaveAsync();

Finally, after the save completes, you can assign a ParseFile into a ParseObject just like any other piece of data:

var jobApplication = new ParseObject("JobApplication");
jobApplication["applicantName"] = "Joe Smith";
jobApplication["applicantResumeFile"] = file;
await jobApplication.SaveAsync();

Retrieving it back involves downloading the resource at the ParseFile’s Url. Here we retrieve the resume file off another JobApplication object:

var applicantResumeFile = anotherApplication.Get<ParseFile>("applicantResumeFile");
string resumeText = await new HttpClient().GetStringAsync(applicantResumeFile.Url);

Progress

It’s easy to get the progress of ParseFile uploads by passing a Progress object to SaveAsync. For example:

byte[] data = System.Text.Encoding.UTF8.GetBytes("Working at Parse is great!");
ParseFile file = new ParseFile("resume.txt", data);

await file.SaveAsync(new Progress<ParseUploadProgressEventArgs>(e => {
    // Check e.Progress to get the progress of the file upload
}));

You can delete files that are referenced by objects using the REST API. You will need to provide the master key in order to be allowed to delete a file.

If your files are not referenced by any object in your app, it is not possible to delete them through the REST API. You may request a cleanup of unused files in your app’s Settings page. Keep in mind that doing so may break functionality which depended on accessing unreferenced files through their URL property. Files that are currently associated with an object will not be affected.

GeoPoints

Parse allows you to associate real-world latitude and longitude coordinates with an object. Adding a ParseGeoPoint to a ParseObject allows queries to take into account the proximity of an object to a reference point. This allows you to easily do things like find out what user is closest to another user or which places are closest to a user.

ParseGeoPoint

To associate a point with an object you first need to create a ParseGeoPoint. For example, to create a point with latitude of 40.0 degrees and -30.0 degrees longitude:

var point = new ParseGeoPoint(40.0, -30.0);

This point is then stored in the object as a regular field.

placeObject["location"] = point;

Note: Currently only one key in a class may be a ParseGeoPoint.

Geo Queries

Now that you have a bunch of objects with spatial coordinates, it would be nice to find out which objects are closest to a point. This can be done by adding another restriction to a ParseQuery using WhereNear. Getting a list of ten places that are closest to a user may look something like:

// User's location
var userGeoPoint = ParseUser.CurrentUser.Get<ParseGeoPoint>("location");
// Create a query for places
var query = ParseObject.GetQuery("PlaceObject");
//Interested in locations near user.
query = query.WhereNear("location", userGeoPoint);
// Limit what could be a lot of points.
query = query.Limit(10);
// Final list of nearby places
var placeObjects = await query.FindAsync();

At this point placesObjects will be an IEnumerable<ParseObject> of PlaceObjects ordered by distance (nearest to farthest) from userGeoPoint.

To limit the results using distance check out WhereWithinDistance,.

It’s also possible to query for the set of objects that are contained within a particular area. To find the objects in a rectangular bounding box, add the WhereWithinGeoBox restriction to your ParseQuery.

var swOfSF = new ParseGeoPoint(37.708813, -122.526398);
var neOfSF = new ParseGeoPoint(37.822802, -122.373962);
var query = ParseObject.GetQuery("PizzaPlaceObject")
    .WhereWithinGeoBox("location", swOfSF, neOfSF);
var pizzaPlacesInSF = await query.FindAsync();

Geo Distances

Parse makes it easy to find the distance between two GeoPoints and query based upon that distance. For example, to get a distance in kilometers between two points, you can use the DistanceTo method:

ParseGeoPoint p1 = /* Some location */;
ParseGeoPoint p2 = /* Some other location */;
double distanceInKm = p1.DistanceTo(p2).Kilometers;

You can also query for ParseObjects within a radius using a ParseGeoDistance. For example, to find all places within 5 miles of a user, you would use the WhereWithinDistance method:

ParseGeoPoint userGeoPoint = ParseUser.CurrentUser.Get<ParseGeoPoint>("location");
ParseQuery<ParseObject> query = ParseObject.GetQuery("PlaceObject")
    .WhereWithinDistance("location", userGeoPoint, ParseGeoDistance.FromMiles(5));
IEnumerable<ParseObject> nearbyLocations = await query.FindAsync();
// nearbyLocations contains PlaceObjects within 5 miles of the user's location

At this point, nearbyLocations will be an array of objects ordered by distance (nearest to farthest) from userGeoPoint. Note that if an additional OrderBy() constraint is applied, it will take precedence over the distance ordering.

Caveats

At the moment there are a couple of things to watch out for:

1. Each ParseObject class may only have one key with a ParseGeoPoint object.
2. Using the whereNear constraint will also limit results to within 100 miles.
3. Points should not equal or exceed the extreme ends of the ranges. Latitude should not be -90.0 or 90.0. Longitude should not be -180.0 or 180.0. Attempting to set latitude or longitude out of bounds will cause an error.

Push Notifications

Push Notifications are a great way to keep your users engaged and informed about your app. You can reach your entire user base quickly and effectively. This guide will help you through the setup process and the general usage of Parse to send push notifications.

If you haven’t installed the SDK yet, please head over to the Push QuickStart to get our SDK up and running.

Setting Up Push

Currently .NET SDK can receive push on Windows 8, Windows Phone 8, Xamarin iOS and Xamarin Android.

Push on Windows 8

If you want to start using push on Windows 8, start by completing the Windows 8 Push tutorial to learn how to configure your app. Come back to this guide afterwards to learn more about the push features offered by Parse.

Push on Windows Phone 8

Windows Phone 8 supports authenticated and unauthenticated push notifications. Authenticated push notifications are not supported at this time. In the meantime, enjoy toast push notifications without any required setup. Some things you need to keep in mind:

• The communication between Parse and Microsoft’s cloud is unencrypted. The communication between your device and Parse will always be secure.
• You are limited to 500 pushes per day per subscription.

Push on Xamarin iOS

If you want to start using push on Xamarin iOS, start by completing the iOS Push tutorial to learn how to configure your push certificate.

Push on Xamarin Android

If you want to start using push on Unity Android, start by completing Android Push tutorial to learn how to configure your app.

Installations

Every Parse application installed on a device registered for push notifications has an associated Installation object. The Installation object is where you store all the data needed to target push notifications. For example, in a baseball app, you could store the teams a user is interested in to send updates about their performance. Saving the Installation object is also required for tracking push-related app open events.

On .NET, Installation objects are available through the ParseInstallation class, a subclass of ParseObject. It uses the same API for storing and retrieving data. To access the current Installation object from your .NET app, use the ParseInstallation.CurrentInstallation property.

While it is possible to modify a ParseInstallation just like you would a ParseObject, there are several special fields that help manage and target devices.

• channels: An IEnumerable<string> of the channels to which a device is currently subscribed. In .NET, this field is accessible through the Channels property.
• timeZone: The current time zone where the target device is located. This field is readonly and can be accessed via the TimeZone property. This value is synchronized every time an Installation object is saved from the device.
• localeIdentifier: The locale identifier of the device in the format [language code]-[COUNTRY CODE]. The language codes are two-letter lowercase ISO language codes (such as “en”) as defined by ISO 639-1. The country codes are two-letter uppercase ISO country codes (such as “US”) as defined by ISO 3166-1. This value is synchronized every time a ParseInstallation object is saved from the device (readonly).
• deviceType: The type of device, “ios”, “android”, “winrt”, “winphone”, or “dotnet”. This field is readonly and can be accessed via the DeviceType property.
• pushType: This field is reserved for directing Parse to the push delivery network to be used. If the device is registered to receive pushes via FCM, this field will be marked “gcm”. If this device is not using FCM, it will be blank (readonly).
• installationId: Unique Id for the device used by Parse. This field is readonly and can be accessed via the InstallationId property.
• deviceToken: The Apple generated token used for iOS devices, or Google generated token used for Android devices (readonly).
• channelUris: The Microsoft-generated push URIs for Windows devices. This field is readonly and can be accessed via the DeviceUris property.
• appName: The display name of the client application to which this installation belongs. This field is readonly and can be accessed via the AppName property.
• appVersion: The version string of the client application to which this installation belongs. This field is readonly and can be accessed via the AppVersion property.
• parseVersion: The version of the Parse SDK which this installation uses. This field is readonly and can be accessed via the ParseVersion property.
• appIdentifier: A unique identifier for this installation’s client application. This field is readonly and can be accessed via the AppIdentifier property. On Windows 8, this is the Windows.ApplicationModel.Package id; on Windows Phone 8 this is the ProductId; in other .NET applications, this is the ApplicationIdentity of the current AppDomain

Sending Pushes

There are two ways to send push notifications using Parse: channels and advanced targeting. Channels offer a simple and easy to use model for sending pushes, while advanced targeting offers a more powerful and flexible model. Both are fully compatible with each other and will be covered in this section.

Sending notifications is often done from the Parse Dashboard push console, the REST API or from Cloud Code. However, push notifications can also be triggered by the existing client SDKs. If you decide to send notifications from the client SDKs, you will need to set Client Push Enabled in the Push Notifications settings of your Parse app.

However, be sure you understand that enabling Client Push can lead to a security vulnerability in your app. We recommend that you enable Client Push for testing purposes only, and move your push notification logic into Cloud Code when your app is ready to go into production.

You can view your past push notifications on the Parse Dashboard push console for up to 30 days after creating your push. For pushes scheduled in the future, you can delete the push on the push console as long as no sends have happened yet. After you send the push, the push console shows push analytics graphs.

Using Channels

The simplest way to start sending notifications is using channels. This allows you to use a publisher-subscriber model for sending pushes. Devices start by subscribing to one or more channels, and notifications can later be sent to these subscribers. The channels subscribed to by a given Installation are stored in the channels field of the Installation object.

Subscribing to Channels

A channel is identified by a string that starts with a letter and consists of alphanumeric characters, underscores, and dashes. It doesn’t need to be explicitly created before it can be used and each Installation can subscribe to any number of channels at a time.

An installation’s channels can be set using the Channels property of ParseInstallation. For example, in a baseball socre app, we could do:

// When users indicate they are Giants fans, we subscribe them to that channel.
var installation = ParseInstallation.CurrentInstallation;
installation.Channels = new List<string> { "Giants" };
await installation.SaveAsync();

Alternatively, you can insert a channel into Channels without affecting the existing channels using the AddUniqueToList method of ParseObject using the following:

var installation = ParseInstallation.CurrentInstallation;
installation.AddUniqueToList("channels", "Giants");
await installation.SaveAsync();

Finally, ParsePush provides a shorthand for inserting a channel into Channels and saving:

await ParsePush.SubscribeAsync("Giants");

Once subscribed to the “Giants” channel, your Installation object should have an updated channels field.

Unsubscribing from a channel is just as easy:

var installation = ParseInstallation.CurrentInstallation;
installation.RemoveAllFromList("channels" new List<string> { "Giants" });
await installation.SaveAsync();

Or, using ParsePush:

    ParsePush.UnsubscribeAsync("Giants");

The set of subscribed channels is cached in the CurrentInstallation object:

var installation = ParseInstallation.CurrentInstallation
IEnumerable<string> subscribedChannels = installation.Channels;

If you plan on changing your channels from Cloud Code or the data browser, note that you’ll need to call FetchAsync prior to this line in order to get the most recent channels.

Sending Pushes to Channels

In the .NET SDK, the following code can be used to alert all subscribers of the “Giants” channel that their favorite team just scored. This will display a toast notification to Windows users. iOS users will receive a notification in the notification center and Android users will receive a notification in the system tray.

// Send a notification to all devices subscribed to the "Giants" channel.
var push = new ParsePush();
push.Channels = new List<string> {"Giants"};
push.Alert = "The Giants just scored!";
await push.SendAsync();

If you want to target multiple channels with a single push notification, you can use any IEnumerable<string> of channels.

Using Advanced Targeting

While channels are great for many applications, sometimes you need more precision when targeting the recipients of your pushes. Parse allows you to write a query for any subset of your Installation objects using the querying API and to send them a push.

Since ParseInstallation is a subclass of ParseObject, you can save any data you want and even create relationships between Installation objects and your other objects. This allows you to send pushes to a very customized and dynamic segment of your user base.

Saving Installation Data

Storing data on an Installation object is just as easy as storing any other data on Parse. In our Baseball app, we could allow users to get pushes about game results, scores and injury reports.

// Store the category of push notifications the user would like to receive.
var installation = ParseInstallation.CurrentInstallation;
installation["scores"] = true;
installation["gameResults"] = true;
installation["injuryReports"] = true;
await installation.SaveAsync();

You can even create relationships between your Installation objects and other classes saved on Parse. To associate an Installation with a particular user, for example, you can simply store the current user on the ParseInstallation.

// Associate the device with a user
var installation = ParseInstallation.CurrentInstallation;
installation["user"] = ParseUser.CurrentUser;
await installation.SaveAsync();

Sending Pushes to Queries

Once you have your data stored on your Installation objects, you can use a ParseQuery to target a subset of these devices. Installation queries work just like any other Parse query, but we use the special static property ParseInstallation.Query to create it. We set this query on our ParsePush object, before sending the notification.

var push = new ParsePush();
push.Query = from installation in ParseInstallation.Query
             where installation.Get<bool>("injuryReports") == true
             select installation;
push.Alert = "Willie Hayes injured by own pop fly.";
await push.SendAsync();

We can even use channels with our query. To send a push to all subscribers of the “Giants” channel but filtered by those who want score update, we can do the following:

var push = new ParsePush();
push.Query = from installation in ParseInstallation.Query
             where installation.Get<bool>("scores") == true
             select installation;
push.Channels = new List<string> { "Giants" };
push.Alert = "Giants scored against the A's! It's now 2-2.";
await push.SendAsync();

Alternatively, we can use a query that constrains “channels” directly:

var push = new Parse.Push();
push.Query = from installation in ParseInstallation.Query
             where installation.Get<bool>("scores") == true
             where installation.Channels.Contains("Giants")
             select installation;
push.Alert = "Giants scored against the A's! It's now 2-2.";
await push.SendAsync();

If we store relationships to other objects in our Installation class, we can also use those in our query. For example, we could send a push notification to all users near a given location like this.

// Find users in the Seattle metro area
var userQuery = ParseUser.Query.WhereWithinDistance(
    "location",
    marinersStadium,
    ParseGeoDistance.FromMiles(1));
var push= new ParsePush();
push.Query = from installation in ParseInstallation.Query
             join user in userQuery on installation["user"] equals user
             select installation;
push.Alert = "Mariners lost? Free conciliatory hotdogs at the Parse concession stand!";
await push.SendAsync();

Sending Options

Push notifications can do more than just send a message. On Xamarin, Windows, Windows Phone 8, pushes can also include a title, as well as any custom data you wish to send. An expiration date can also be set for the notification in case it is time sensitive.

Customizing your Notifications

If you want to send more than just a message, you will need to use an IDictionary<string, object> to package all of the data. There are some reserved fields that have a special meaning.

• alert: the notification’s message.
• badge: (iOS only) the value indicated in the top right corner of the app icon. This can be set to a value or to Increment in order to increment the current value by 1.
• sound: (iOS only) the name of a sound file in the application bundle.
• content-available: (iOS only) If you are a writing an app using the Remote Notification Background Mode introduced in iOS7 (a.k.a. “Background Push”), set this value to 1 to trigger a background download.
• category: (iOS only) the identifier of the UNNotification​Category for this push notification.
• uri: (Android only) an optional field that contains a URI. When the notification is opened, an Activity associated with opening the URI is launched.
• title: (Android, Windows 8, and Windows Phone 8 only) the value displayed in the Android system tray or Windows toast notification.

For example, to send a notification that contains a title, you can do the following:

var push = new ParsePush();
push.Channels = new List<string> {"Mets"};
push.Data = new Dictionary<string, object> {
  {"title", "Score Alert"}
  {"alert", "The Mets scored! The game is now tied 1-1!"},
};
await push.SendAsync();

Setting an Expiration Date

When a user’s device is turned off or not connected to the internet, push notifications cannot be delivered. If you have a time sensitive notification that is not worth delivering late, you can set an expiration date. This avoids needlessly alerting users of information that may no longer be relevant.

There are two properties provided by the ParsePush class to allow setting an expiration date for your notification. The first is Expiration which simply takes a DateTime? specifying when Parse should stop trying to send the notification.

var push = new ParsePush();
push.Expiration = new DateTime(2015, 8, 14);
push.Alert = "Season tickets on sale until August 14th!";
await push.SendAsync();

There is however a caveat with this method. Since device clocks are not guaranteed to be accurate, you may end up with inaccurate results. For this reason, the ParsePush class also provides the ExpirationInterval property which accepts a TimeSpan. The notification will expire after the specified interval has elapsed.

var push = new ParsePush();
push.ExpirationInterval = TimeSpan.FromDays(7);
push.Alert = "Season tickets on sale until next week!";
await push.SendAsync();

Targeting by Platform

If you build a cross platform app, it is possible you may only want to target one operating system. There are two methods provided to filter which of these devices are targeted. Note that all platforms are targeted by default.

The following example would send a different notification to Android, iOS, and Windows users.

// Notification for Android users
var androidPush = new ParsePush();
androidPush.Alert = "Your suitcase has been filled with tiny robots!";
androidPush.Query = from installation in ParseInstallation.Query
                    where installation.Channels.Contains("suitcaseOwners")
                    where installation.DeviceType == "android"
                    select installation;
await androidPush.SendAsync();

// Notification for iOS users
var iosPush = new ParsePush();
iosPush.Alert = "Your suitcase has been filled with tiny apples!";
iosPush.Query = from installation in ParseInstallation.Query
                where installation.Channels.Contains("suitcaseOwners")
                where installation.DeviceType == "ios"
                select installation;
await iosPush.SendAsync();

// Notification for Windows 8 users
var winPush = new ParsePush();
winPush.Alert = "Your suitcase has been filled with tiny glass!";
winPush.Query = from installation in ParseInstallation.Query
                where installation.Channels.Contains("suitcaseOwners")
                where installation.DeviceType == "winrt"
                select installation;
await winPush.SendAsync();

// Notification for Windows Phone 8 users
var wpPush = new ParsePush();
wpPush.Alert = "Your suitcase is very hip; very metro.";
wpPush.Query = from installation in ParseInstallation.Query
               where installation.Channels.Contains("suitcaseOwners")
               where installation.DeviceType == "winphone"
               select installation;
await wpPush.SendAsync();

Scheduling Pushes

Sending scheduled push notifications is not currently supported by the .NET SDK. Take a look at the REST API, JavaScript SDK or the Parse Dashboard push console.

Receiving Pushes

Responding to the Payload

If your app is running while a push notification is received, the ParsePush.ParsePushNotificationReceived event is fired. You can register for this event. This event provides ParsePushNotificationEventArgs. When Parse sends a toast notification, it embeds the JSON payload in the notification.

ParsePush.ParsePushNotificationReceived += (sender, args) => {
  var payload = args.Payload;
  object objectId;
  if (payload.TryGetValue("objectId", out objectId)) {
    DisplayRichMessageWithObjectId(objectId as string);
  }
};

In Xamarin iOS, you need to call ParsePush.HandlePush inside AppDelegate.ReceivedRemoteNotification

public override void ReceivedRemoteNotification(UIApplication application, NSDictionary userInfo) {
  base.ReceivedRemoteNotification(application, userInfo);

  // We need this to fire userInfo into ParsePushNotificationReceived.
  ParsePush.HandlePush(userInfo);
}

In Windows 8, you may also receive the JSON payload from the LaunchActivatedEventArgs passed to your application’s OnLaunched event.

protected override void OnLaunched(LaunchActivatedEventArgs args) {
  var json = ParsePush.PushJson(args);
  object objectId;
  if (json.TryGetValue("objectId", out objectId)) {
    DisplayRichMessageWithObjectId(objectId as string);
  }
};

In Windows Phone 8, this code would instead be in your page’s OnNavigatedTo event:

public override void OnNavigatedTo(NavigationEventArgs args) {
  var json = ParsePush.PushJson(args);
  object objectId;
  if (json.TryGetValue("objectId", out objectId)) {
    DisplayRichMessageWithObjectId(objectId as string);
  }
}

Tracking Pushes and App Opens

To track your users’ engagement over time and the effect of push notifications, we provide some hooks in the ParseAnalytics class. In the example above, add the following to your Launching event handler to collect information about when your application was opened, and what triggered it.

ParseAnalytics.TrackAppOpenedAsync(launchArgs);

To track push opens, you should always pass your event handler’s input args to TrackAppOpenedAsync. A null or empty parameter to TrackAppOpenedAsync will track only a standard app-opened event, not the push-opened event. If you don’t track the push-opened event, you will not be able to use advanced analytics features such as push-open graphs and A/B testing.

Please be sure to set up your application to save the Installation object Push open tracking only works when your application’s devices are associated with saved Installation objects.

You can view the open rate for a specific push notification on your Parse Dashboard push console. You can also view your application’s overall app open and push open graphs on the Parse analytics console. Our push open analytics graphs are rendered in real time, so you can easily verify that your application is sending the correct analytics events before your next release.

Tracking on WinRT Applications

On Windows 8, a toast notification can pass a small payload to the launch handler. We take advantage of this to pass a small Parse payload to the app, in order to correlate an app launch with a particular push.

// Override Application.OnLaunched
virtual void OnLaunched(LaunchActivatedEventArgs args) {
    // 'args' contains arguments that are passed to the app
    // during its launch activation from a Toast.
    // More on Toasts: http://msdn.microsoft.com/en-us/library/windows/apps/hh779727.aspx
    ParseAnalytics.TrackAppOpenedAsync(args);
}

Tracking on Windows Phone Applications

You can also track application launches from toast notifications in Windows Phone 8. To track application launches from toasts and tiles, add the following to your App constructor:

this.Startup += (sender, args) => {
  ParseAnalytics.TrackAppOpens(RootFrame);
};

This method will set up event handlers necessary to track all app launches; you should not use TrackAppOpenedAsync if you register event handlers with TrackAppOpens.

Tracking on Xamarin Applications

This feature is not supported yet in Xamarin Applications.

Push Experiments

You can A/B test your push notifications to figure out the best way to keep your users engaged. With A/B testing, you can simultaneously send two versions of your push notification to different devices, and use each version’s push open rates to figure out which one is better. You can test by either message or send time.

A/B Testing

Our web push console guides you through every step of setting up an A/B test.

For each push campaign sent through the Parse web push console, you can allocate a subset of your devices to be in the experiment’s test audience, which Parse will automatically split into two equally-sized experiment groups. For each experiment group, you can specify a different push message. The remaining devices will be saved so that you can send the winning message to them later. Parse will randomly assign devices to each group to minimize the chance for a test to affect another test’s results (although we still don’t recommend running multiple A/B tests over the same devices on the same day).

After you send the push, you can come back to the push console to see in real time which version resulted in more push opens, along with other metrics such as statistical confidence interval. It’s normal for the number of recipients in each group to be slightly different because some devices that we had originally allocated to that experiment group may have uninstalled the app. It’s also possible for the random group assignment to be slightly uneven when the test audience size is small. Since we calculate open rate separately for each group based on recipient count, this should not significantly affect your experiment results.

If you are happy with the way one message performed, you can send that to the rest of your app’s devices (i.e. the “Launch Group”). This step only applies to A/B tests where you vary the message.

Push experiments are supported on all recent Parse SDKs (iOS v1.2.13+, Android v1.4.0+, .NET v1.2.7+). Before running experiments, you must instrument your app with push open tracking.

Experiment Statistics

Parse provides guidance on how to run experiments to achieve statistically significant results.

Test Audience Size

When you setup a push message experiment, we’ll recommend the minimum size of your test audience. These recommendations are generated through simulations based on your app’s historical push open rates. For big push campaigns (e.g. 100k+ devices), this recommendation is usually small subset of your devices. For smaller campaigns (e.g. < 5k devices), this recommendation is usually all devices. Using all devices for your test audience will not leave any remaining devices for the launch group, but you can still gain valuable insight into what type of messaging works better so you can implement similar messaging in your next push campaign.

Confidence Interval

After you send your pushes to experiment groups, we’ll also provide a statistical confidence interval when your experiment has collected enough data to have statistically significant results. This confidence interval is in absolute percentage points of push open rate (e.g. if the open rates for groups A and B are 3% and 5%, then the difference is reported as 2 percentage points). This confidence interval is a measure of how much difference you would expect to see between the two groups if you repeat the same experiment many times.

Just after a push send, when only a small number of users have opened their push notifications, the open rate difference you see between groups A and B could be due to random chance, so it might not be reproducible if you run the same experiment again. After your experiment collects more data over time, we become increasingly confident that the observed difference is a true difference. As this happens, the confidence interval will become narrower, allowing us to more accurately estimate the true difference between groups A and B. Therefore, we recommend that you wait until there is enough data to generate a statistical confidence interval before deciding which group’s push is better.

Push Localization

Localizing your app’s content is a proven way to drive greater engagement. We’ve made it easy to localize your push messages with Push Localization. The latest version of the Parse .NET SDK will detect and store the user’s language in the installation object, and via the web push console you’ll be able to send localized push messages to your users in a single broadcast.

Setup for localized push

To take advantage of Push Localization you will need to make sure you’ve published your app with the Parse .NET SDK version 1.5.5 or greater. Any users of your application running the Parse .NET SDK version 1.5.5 or greater will then be targetable by Push Localization via the web push console.

It’s important to note that for developers who have users running apps with versions of the Parse .NET SDK earlier than 1.5.5 that targeting information for Localized Push will not be available and these users will receive the default message from the push console.

Sending a localized push

Our web push console guides you through every step of setting up a Localized Push.

Troubleshooting

Setting up Push Notifications is often a source of frustration for developers. The process is complicated and invites problems to happen along the way. If you run into issues, try some of these troubleshooting tips.

• Make sure you are using the correct Package SID and client secret, as shown in Step 3 of the Windows 8 Push Quickstart.
• Clean and build your project.
• Check the number of recipients in your Parse Push Console. Does it match the expected number of recipients? Your push might be targeted incorrectly.
• Open your project’s package.appxmanifest file and make sure “Toast Capable” is set to “yes.”* If your app has been released for a while, it’s possible for the recipient estimate on the push composer page to be higher than the pushes sent value on the push results page. The push composer estimate is generated via running your push segment query over your app’s installation table. We do not automatically delete installation objects when the users uninstall your app. When we try to send a push, we detect uninstalled installations and do not include them in the pushes sent value on the results page.
• If you’re receiving push from Unity iOS, refer to iOS Push Troubleshooting Guide.
• If you’re receiving push from Unity Android, refer to Android Push Troubleshooting Guide.

Config

Parse Config

ParseConfig is a way to configure your applications remotely by storing a single configuration object on Parse. It enables you to add things like feature gating or a simple “Message of the Day”. To start using ParseConfig you need to add a few key/value pairs (parameters) to your app on the Parse Config Dashboard.

After that you will be able to fetch the ParseConfig on the client, like in this example:

ParseConfig config = null;
try {
  config = await ParseConfig.GetAsync();
} catch (Exception e) {
  // Something went wrong (e.g. request timed out)
}

Retrieving Config

ParseConfig is built to be as robust and reliable as possible, even in the face of poor internet connections. Caching is used by default to ensure that the latest successfully fetched config is always available. In the below example we use GetAsync to retrieve the latest version of config from the server, and if the fetch fails we can simply fall back to the version that we successfully fetched before via CurrentConfig.

ParseConfig config = null;
try {
  config = await ParseConfig.GetAsync();
  Console.WriteLine("Yay! Config was fetched from the server.");
} catch (Exception e) {
  Console.WriteLine("Failed to fetch. Using Cached Config.");
  config = ParseConfig.CurrentConfig;
}

string welcomeMessage = null;
boolean result = config.TryGetValue("welcomeMessage", out welcomeMessage);
if (!result) {
  Console.WriteLine("Falling back to default message.");
  welcomeMessage = "Welcome!";
}

Console.WriteLine(String.Format("Welcome Messsage From Config = {0}", welcomeMessage));

Current Config

Every ParseConfig instance that you get is always immutable. When you retrieve a new ParseConfig in the future from the network, it will not modify any existing ParseConfig instance, but will instead create a new one and make it available via ParseConfig.CurrentConfig. Therefore, you can safely pass around any ParseConfig object and safely assume that it will not automatically change.

It might be troublesome to retrieve the config from the server every time you want to use it. You can avoid this by simply using the cached CurrentConfig object and fetching the config only once in a while.

public class Helper
{
  private static TimeSpan configRefreshInterval = TimeSpan.FromHours(12);
  private static DateTime? lastFetchedDate;

  // Fetches the config at most once every 12 hours per app runtime
  public static void FetchConfigIfNeeded()
  {
    if (lastFetchedDate == null ||
        DateTime.Now - lastFetchedDate > configRefreshInterval) {
      lastFetchedDate = DateTime.Now;
      ParseConfig.GetAsync();
    }
  }
}

Parameters

ParseConfig supports most of the data types supported by ParseObject:

• string
• Numbers (boolean/int/double/long)
• DateTime
• ParseFile
• ParseGeoPoint
• IList<string, T>
• IDictionary

We currently allow up to 100 parameters in your config and a total size of 128KB across all parameters.

Analytics

Parse provides a number of hooks for you to get a glimpse into the ticking heart of your app. We understand that it’s important to understand what your app is doing, how frequently, and when.

While this section will cover different ways to instrument your app to best take advantage of Parse’s analytics backend, developers using Parse to store and retrieve data can already take advantage of metrics on Parse.

Without having to implement any client-side logic, you can view real-time graphs and breakdowns (by device type, Parse class name, or REST verb) of your API Requests in your app’s dashboard and save these graph filters to quickly access just the data you’re interested in.

App-Open / Push Analytics

Our initial analytics hook allows you to track your application being launched. By adding the following line to your Launching event handler, you’ll be able to collect data on when and how often your application is opened.

ParseAnalytics.TrackAppOpenedAsync();

Custom Analytics

ParseAnalytics also allows you to track free-form events, with a handful of string keys and values. These extra dimensions allow segmentation of your custom events via your app’s Dashboard.

Say your app offers search functionality for apartment listings, and you want to track how often the feature is used, with some additional metadata.

var dimensions = new Dictionary<string, string> {
  // Define ranges to bucket data points into meaningful segments
  { "priceRange", "1000-1500" },
  // Did the user filter the query?
  { "source", "craigslist" },
  // Do searches happen more often on weekdays or weekends?
  { "dayType", "weekday" }
};
// Send the dimensions to Parse along with the 'search' event
ParseAnalytics.TrackEventAsync("search", dimensions);

ParseAnalytics can even be used as a lightweight error tracker — simply invoke the following and you’ll have access to an overview of the rate and frequency of errors, broken down by error code, in your application:

var errDimensions = new Dictionary<string, string> {
  { "code", Convert.ToString(error.Code) }
};
ParseAnalytics.TrackEventAsync("error", errDimensions );

Note that Parse currently only stores the first eight dimension pairs per call to ParseAnalytics.TrackEventAsync().

Data

We’ve designed the Parse SDKs so that you typically don’t need to worry about how data is saved while using the client SDKs. Simply add data to the Parse Object, and it’ll be saved correctly.

Nevertheless, there are some cases where it’s useful to be aware of how data is stored on the Parse platform.

Data Storage

Internally, Parse stores data as JSON, so any datatype that can be converted to JSON can be stored on Parse. Refer to the Data Types in Objects section of this guide to see platform-specific examples.

Keys including the characters $ or ., along with the key __type key, are reserved for the framework to handle additional types, so don’t use those yourself. Key names must contain only numbers, letters, and underscore, and must start with a letter. Values can be anything that can be JSON-encoded.

Data Type Lock-in

When a class is initially created, it doesn’t have an inherent schema defined. This means that for the first object, it could have any types of fields you want.

However, after a field has been set at least once, that field is locked into the particular type that was saved. For example, if a User object is saved with field name of type String, that field will be restricted to the String type only (the server will return an error if you try to save anything else).

One special case is that any field can be set to null, no matter what type it is.

The Data Browser

The Data Browser is the web UI where you can update and create objects in each of your apps. Here, you can see the raw JSON values that are saved that represents each object in your class.

When using the interface, keep in mind the following:

• The objectId, createdAt, updatedAt fields cannot be edited (these are set automatically).
• The value “(empty)” denotes that the field has not been set for that particular object (this is different than null).
• You can remove a field’s value by hitting your Delete key while the value is selected.

The Data Browser is also a great place to test the Cloud Code validations contained in your Cloud Code functions (such as beforeSave). These are run whenever a value is changed or object is deleted from the Data Browser, just as they would be if the value was changed or deleted from your client code.

Importing Data

You may import data into your Parse app by using CSV or JSON files. To create a new class with data from a CSV or JSON file, go to the Data Browser and click the “Import” button on the left hand column.

The JSON format is an array of objects in our REST format or a JSON object with a results that contains an array of objects. It must adhere to the JSON standard. A file containing regular objects could look like:

{ "results": [
  {
    "score": 1337,
    "playerName": "Sean Plott",
    "cheatMode": false,
    "createdAt": "2022-01-01T12:23:45.678Z",
    "updatedAt": "2022-01-01T12:23:45.678Z",
    "objectId": "fchpZwSuGG"
  }]
}

Objects in either format should contain keys and values that also satisfy the following:

• Key names must contain only numbers, letters, and underscore, and must start with a letter.
• No value may contain a hard newline ‘\n’.

Normally, when objects are saved to Parse, they are automatically assigned a unique identifier through the objectId field, as well as a createdAt field and updatedAt field which represent the time that the object was created and last modified in your Parse Server. These fields can be manually set when data is imported from a JSON file. Please keep in mind the following:

• Use a unique 10 character alphanumeric string as the value of your objectId fields.
• Use a UTC timestamp in the ISO 8601 format when setting a value for the createdAt field or the updatedAt field.

In addition to the exposed fields, objects in the Parse User class can also have the bcryptPassword field set. The value of this field is a String that is the bcrypt hashed password + salt in the modular crypt format described in this StackOverflow answer. Most OpenSSL based bcrypt implementations should have built-in methods to produce these strings.

A file containing a User object could look like:

{ "results":
  [{
    "username": "cooldude",
    "createdAt": "1983-09-13T22:42:30.548Z",
    "updatedAt": "2015-09-04T10:12:42.137Z",
    "objectId": "ttttSEpfXm",
    "sessionToken": "dfwfq3dh0zwe5y2sqv514p4ib",
    "bcryptPassword": "$2a$10$ICV5UeEf3lICfnE9W9pN9.O9Ved/ozNo7G83Qbdk5rmyvY8l16MIK"
  }]
}

Note that in CSV the import field types are limited to String, Boolean, and Number.

Exporting your Data

You can request an export of your data at any time from your app’s Settings page. The data export runs at a lower priority than production queries, so if your app is still serving queries, production traffic will always be given a higher priority, which may slow down the delivery of your data export.

Export Formats

Each collection will be exported in the same JSON format used by our REST API and delivered in a single zipped file. Since data is stored internally as JSON, this allows us to ensure that the export closely matches how the data is saved to Parse. Other formats such as CSV cannot represent all of the data types supported by Parse without losing information. If you’d like to work with your data in CSV format, you can use any of the JSON-to-CSV converters available widely on the web.

Offline Analysis

For offline analysis of your data, we highly recommend using alternate ways to access your data that do not require extracting the entire collection at once. For example, you can try exporting only the data that has changed since your last export. Here are some ways of achieving this:

• Use the JavaScript SDK in a node app. Parse.Query.each() will allow you to extract every single object that matches a query. You can use date constraints to make sure the query only matches data that has been updated since you last ran this app. Your node app can write this data to disk for offline analysis.

• Use the REST API in a script. You can run queries against your class and use skip/limit to page through results, which can then be written to disk for offline analysis. You can again use date constraints to make sure only newly updated data is extracted.

• If the above two options do not fit your needs, you can try using the Data Browser to export data selectively. Use the Funnel icon to create a filter for the specific data that you need to export, such as newly updated objects. Once the filter has been applied, click on the Export data icon on the upper right of your Data Browser. This type of export will only include the objects that match your criteria.

Relations

There are three kinds of relationships. One-to-one relationships enable one object to be associated with another object. One-to-many relationships enable one object to have many related objects. Finally, many-to-many relationships enable complex relationships among many objects.

There are four ways to build relationships in Parse:

One-to-Many

When you’re thinking about one-to-many relationships and whether to implement Pointers or Arrays, there are several factors to consider. First, how many objects are involved in this relationship? If the “many” side of the relationship could contain a very large number (greater than 100 or so) of objects, then you have to use Pointers. If the number of objects is small (fewer than 100 or so), then Arrays may be more convenient, especially if you typically need to get all of the related objects (the “many” in the “one-to-many relationship”) at the same time as the parent object.

Using Pointers

Let’s say we have a game app. The game keeps track of the player’s score and achievements every time she chooses to play. In Parse, we can store this data in a single Game object. If the game becomes incredibly successful, each player will store thousands of Game objects in the system. For circumstances like this, where the number of relationships can be arbitrarily large, Pointers are the best option.

Suppose in this game app, we want to make sure that every Game object is associated with a Parse User. We can implement this like so:

var game = new ParseObject("Game");
game["createdBy"] = ParseUser.CurrentUser;

We can obtain all of the Game objects created by a Parse User with a query:

var query = ParseObject.getQuery("Game").WhereEqualTo("createdBy", ParseUser.CurrentUser);

And, if we want to find the Parse User who created a specific Game, that is a lookup on the createdBy key:

// say we have a Game object
ParseObject game = ...

// getting the user who created the Game
ParseUser user = game["createdBy"];

For most scenarios, Pointers will be your best bet for implementing one-to-many relationships.

Using Arrays

Arrays are ideal when we know that the number of objects involved in our one-to-many relationship are going to be small. Arrays will also provide some productivity benefit via the includeKey parameter. Supplying the parameter will enable you to obtain all of the “many” objects in the “one-to-many” relationship at the same time that you obtain the “one” object. However, the response time will be slower if the number of objects involved in the relationship turns out to be large.

Suppose in our game, we enabled players to keep track of all the weapons their character has accumulated as they play, and there can only be a dozen or so weapons. In this example, we know that the number of weapons is not going to be very large. We also want to enable the player to specify the order in which the weapons will appear on screen. Arrays are ideal here because the size of the array is going to be small and because we also want to preserve the order the user has set each time they play the game:

Let’s start by creating a column on our Parse User object called weaponsList.

Now let’s store some Weapon objects in the weaponsList:

// let's say we have four weapons
var scimitar = ...
var plasmaRifle = ...
var grenade = ...
var bunnyRabbit = ...

// stick the objects in an array
var weapons = new List<ParseObject>();
weapons.Add(scimitar);
weapons.Add(plasmaRifle);
weapons.Add(grenade);
weapons.Add(bunnyRabbit);

// store the weapons for the user
var user = ParseUser.CurrentUser;
user.AddRangeToList("weaponsList", weapons);

Later, if we want to retrieve the Weapon objects, it’s just one line of code:

var weapons = ParseUser.CurrentUser.Get<IList<Object>>("weaponsList");

Sometimes, we will want to fetch the “many” objects in our one-to-many relationship at the same time as we fetch the “one” object. One trick we could employ is to use the includeKey (or include in Android) parameter whenever we use a Parse Query to also fetch the array of Weapon objects (stored in the weaponsList column) along with the Parse User object:

// set up our query for a User object
var userQuery = ParseUser.Query;

// configure any constraints on your query...
// for example, you may want users who are also playing with or against you

// tell the query to fetch all of the Weapon objects along with the user
// get the "many" at the same time that you're getting the "one"
userQuery = userQuery.Include("weaponsList");

// execute the query
IEnumerable<ParseUser> results = await userQuery.FindAsync();
// results contains all of the User objects, and their associated Weapon objects, too

You can also get the “one” side of the one-to-many relationship from the “many” side. For example, if we want to find all Parse User objects who also have a given Weapon, we can write a constraint for our query like this:

// add a constraint to query for whenever a specific Weapon is in an array
userQuery = userQuery.WhereEqualTo("weaponsList", scimitar);

// or query using an array of Weapon objects...
userQuery = userQuery.WhereContainedIn("weaponsList", arrayOfWeapons);

Many-to-Many

Now let’s tackle many-to-many relationships. Suppose we had a book reading app and we wanted to model Book objects and Author objects. As we know, a given author can write many books, and a given book can have multiple authors. This is a many-to-many relationship scenario where you have to choose between Arrays, Parse Relations, or creating your own Join Table.

The decision point here is whether you want to attach any metadata to the relationship between two entities. If you don’t, Parse Relation or using Arrays are going to be the easiest alternatives. In general, using arrays will lead to higher performance and require fewer queries. If either side of the many-to-many relationship could lead to an array with more than 100 or so objects, then, for the same reason Pointers were better for one-to-many relationships, Parse Relation or Join Tables will be better alternatives.

On the other hand, if you want to attach metadata to the relationship, then create a separate table (the “Join Table”) to house both ends of the relationship. Remember, this is information about the relationship, not about the objects on either side of the relationship. Some examples of metadata you may be interested in, which would necessitate a Join Table approach, include:

Using Parse Relations

Using Parse Relations, we can create a relationship between a Book and a few Author objects. In the Data Browser, you can create a column on the Book object of type relation and name it authors.

After that, we can associate a few authors with this book:

// let’s say we have a few objects representing Author objects
var authorOne = ...
var authorTwo = ...
var authorThree = ...

// now we create a book object
var book = new ParseObject("Book");

// now let’s associate the authors with the book
// remember, we created a "authors" relation on Book
var relation = book.GetRelation<ParseObject>("authors");
relation.Add(authorOne);
relation.Add(authorTwo);
relation.Add(authorThree);

// now save the book object
await book.SaveAsync();

To get the list of authors who wrote a book, create a query:

// suppose we have a book object
var book = ...

// create a relation based on the authors key
var relation = book.GetRelation<ParseObject>("authors");

// generate a query based on that relation
var query = relation.Query;

// now execute the query

Perhaps you even want to get a list of all the books to which an author contributed. You can create a slightly different kind of query to get the inverse of the relationship:

// suppose we have a author object, for which we want to get all books
var author = ...

// first we will create a query on the Book object
var query = ParseObject.GetQuery("Book");

// now we will query the authors relation to see if the author object we have
// is contained therein
query = query.WhereEqualTo("authors", author);

Using Join Tables

There may be certain cases where we want to know more about a relationship. For example, suppose we were modeling a following/follower relationship between users: a given user can follow another user, much as they would in popular social networks. In our app, we not only want to know if User A is following User B, but we also want to know when User A started following User B. This information could not be contained in a Parse Relation. In order to keep track of this data, you must create a separate table in which the relationship is tracked. This table, which we will call Follow, would have a from column and a to column, each with a pointer to a Parse User. Alongside the relationship, you can also add a column with a Date object named date.

Now, when you want to save the following relationship between two users, create a row in the Follow table, filling in the from, to, and date keys appropriately:

// suppose we have a user we want to follow
ParseUser otherUser = ...

// create an entry in the Follow table
var follow = new ParseObject("Follow");
follow["from"] = ParseUser.CurrentUser;
follow["to"] = otherUser;
follow["date"] = DateTime.UtcNow;
await follow.SaveAsync();

If we want to find all of the people we are following, we can execute a query on the Follow table:

// set up the query on the Follow table
ParseQuery<ParseObject> query = ParseQuery.getQuery("Follow");
query = query.WhereEqualTo("from", ParseUser.CurrentUser);

// execute the query
IEnumerable<ParseObject> results = await query.FindAsync();

It’s also pretty easy to find all the users that are following the current user by querying on the to key:

// create an entry in the Follow table
var query = ParseObject.GetQuery("Follow")
    .WhereEqualTo("to", ParseUser.CurrentUser);
IEnumerable<ParseObject> results = await query.FindAsync();

Using an Array

Arrays are used in Many-to-Many relationships in much the same way that they are for One-to-Many relationships. All objects on one side of the relationship will have an Array column containing several objects on the other side of the relationship.

Suppose we have a book reading app with Book and Author objects. The Book object will contain an Array of Author objects (with a key named authors). Arrays are a great fit for this scenario because it’s highly unlikely that a book will have more than 100 or so authors. We will put the Array in the Book object for this reason. After all, an author could write more than 100 books.

Here is how we save a relationship between a Book and an Author.

// let's say we have an author
var author = ...

// and let's also say we have an book
var book = ...

// add the author to the authors list for the book
book.AddToList("authors", author);

Because the author list is an Array, you should use the includeKey (or include on Android) parameter when fetching a Book so that Parse returns all the authors when it also returns the book:

// set up our query for the Book object
var bookQuery = ParseObject.GetQuery("Book");

// configure any constraints on your query...
// tell the query to fetch all of the Author objects along with the Book
bookQuery = bookQuery.Include("authors");

// execute the query
IEnumerable<ParseObject> books= await bookQuery.FindAsync();

At that point, getting all the Author objects in a given Book is a pretty straightforward call:

var authorList = book.Get<List<ParseObject>>("authors");

Finally, suppose you have an Author and you want to find all the Book objects in which she appears. This is also a pretty straightforward query with an associated constraint:

// set up our query for the Book object
var bookQuery = ParseObject.GetQuery("Book");

// configure any constraints on your query...
bookQuery = bookQuery.WhereEqualTo("authors", author);

// tell the query to fetch all of the Author objects along with the Book
bookQuery = bookQuery.Include("authors");

// execute the query
IEnumerable<ParseObject> books = await bookQuery.FindAsync();

One-to-One

In Parse, a one-to-one relationship is great for situations where you need to split one object into two objects. These situations should be rare, but two examples include:

• Limiting visibility of some user data. In this scenario, you would split the object in two, where one portion of the object contains data that is visible to other users, while the related object contains data that is private to the original user (and protected via ACLs).
• Splitting up an object for size. In this scenario, your original object size is too large, so you decide to create a secondary object to house extra data. It is usually better to design your data model to avoid objects this large, rather than splitting them up. If you can’t avoid doing so, you can also consider storing large data in a Parse File.

Thank you for reading this far. We apologize for the complexity. Modeling relationships in data is a hard subject, in general. But look on the bright side: it’s still easier than relationships with people.

Handling Errors

Parse has a few simple patterns for surfacing errors and handling them in your code.

There are two types of errors you may encounter. The first is those dealing with logic errors in the way you’re using the SDK. These types of errors result in general Exception being raised. For an example take a look at the following code:

var user = new ParseUser();
await user.SignUpAsync();

This will throw an InvalidOperationException because SignUpAsync was called without first setting the required properties (Username and Password).

The second type of error is one that occurs when interacting with Parse Server over the network. These errors are either related to problems connecting to the cloud or problems performing the requested operation. Let’s take a look at another example:

await ParseObject.GetQuery("Note").GetAsync("thisObjectIdDoesntExist");

In the above code, we try to fetch an object with a non-existent ObjectId. Parse Server will return an error – so here’s how to handle it properly:

try
{
    await ParseObject.GetQuery("Note").GetAsync(someObjectId);
    // Everything went fine!
}
catch (ParseException e)
{
    if (e.Code == ParseException.ErrorCode.ObjectNotFound)
    {
        // Uh oh, we couldn't find the object!
    }
    else
    {
        // Some other error occurred
    }
}

By default, all connections have a timeout of 10 seconds, so tasks will not hang indefinitely.

For a list of all possible ErrorCode types, scroll down to Error Codes, or see the ParseException.ErrorCode section of the .NET API.

Security

As your app development progresses, you will want to use Parse’s security features in order to safeguard data. This document explains the ways in which you can secure your apps.

If your app is compromised, it’s not only you as the developer who suffers, but potentially the users of your app as well. Continue reading for our suggestions for sensible defaults and precautions to take before releasing your app into the wild.

Client vs. Server

When an app first connects to Parse, it identifies itself with an Application ID and a Client key (or REST Key, or .NET Key, or JavaScript Key, depending on which platform you’re using). These are not secret and by themselves they do not secure an app. These keys are shipped as a part of your app, and anyone can decompile your app or proxy network traffic from their device to find your client key. This exploit is even easier with JavaScript — one can simply “view source” in the browser and immediately find your client key.

This is why Parse has many other security features to help you secure your data. The client key is given out to your users, so anything that can be done with just the client key is doable by the general public, even malicious hackers.

The master key, on the other hand, is definitely a security mechanism. Using the master key allows you to bypass all of your app’s security mechanisms, such as class-level permissions and ACLs. Having the master key is like having root access to your app’s servers, and you should guard your master key with the same zeal with which you would guard your production machines’ root password.

The overall philosophy is to limit the power of your clients (using client keys), and to perform any sensitive actions requiring the master key in Cloud Code. You’ll learn how to best wield this power in the section titled Implementing Business Logic in Cloud Code.

A final note: It is recommended to setup HTTPS and SSL in your server, to avoid man-in-the-middle attacks, but Parse works fine as well with non-HTTPS connections.

Class-Level Permissions

The second level of security is at the schema and data level. Enforcing security measures at this level will restrict how and when client applications can access and create data on Parse. When you first begin developing your Parse application, all of the defaults are set so that you can be a more productive developer. For example:

• A client application can create new classes on Parse
• A client application can add fields to classes
• A client application can modify or query for objects on Parse

You can configure any of these permissions to apply to everyone, no one, or to specific users or roles in your app. Roles are groups that contain users or other roles, which you can assign to an object to restrict its use. Any permission granted to a role is also granted to any of its children, whether they are users or other roles, enabling you to create an access hierarchy for your apps. Each of the Parse guides includes a detailed description of employing Roles in your apps.

Once you are confident that you have the right classes and relationships between classes in your app, you should begin to lock it down by doing the following:

Almost every class that you create should have these permissions tweaked to some degree. For classes where every object has the same permissions, class-level settings will be most effective. For example, one common use case entails having a class of static data that can be read by anyone but written by no one.

Restricting class creation

As a start, you can configure your application so that clients cannot create new classes on Parse. This is done by setting the key allowClientClassCreation to false in your ParseServer configuration. See the project Readme for an overview of Configuring your ParseServer. Once restricted, classes may only be created from the Data Browser or with a the masterKey. This will prevent attackers from filling your database with unlimited, arbitrary new classes.

Enforcing Private Users

Requires Parse Server 5.0.0+

By default, Parse Server creates Users with public read access. This allows other users, and un-authenticated users, to read data such as email. When moving to production, set the key enforcePrivateUsers to true, as this will remove the public read access to new users.

Configuring Class-Level Permissions

Parse lets you specify what operations are allowed per class. This lets you restrict the ways in which clients can access or modify your classes. To change these settings, go to the Data Browser, select a class, and click the “Security” button.

You can configure the client’s ability to perform each of the following operations for the selected class:

• Read:

  • Get: With Get permission, users can fetch objects in this table if they know their objectIds.

  • Find: Anyone with Find permission can query all of the objects in the table, even if they don’t know their objectIds. Any table with public Find permission will be completely readable by the public, unless you put an ACL on each object.

• Write:

  • Update: Anyone with Update permission can modify the fields of any object in the table that doesn’t have an ACL. For publicly readable data, such as game levels or assets, you should disable this permission.

  • Create: Like Update, anyone with Create permission can create new objects of a class. As with the Update permission, you’ll probably want to turn this off for publicly readable data.

  • Delete: With this permission, people can delete any object in the table that doesn’t have an ACL. All they need is its objectId.

• Add fields: Parse classes have schemas that are inferred when objects are created. While you’re developing your app, this is great, because you can add a new field to your object without having to make any changes on the backend. But once you ship your app, it’s very rare to need to add new fields to your classes automatically. You should pretty much always turn off this permission for all of your classes when you submit your app to the public.

For each of the above actions, you can grant permission to all users (which is the default), or lock permissions down to a list of roles and users. For example, a class that should be available to all users would be set to read-only by only enabling get and find. A logging class could be set to write-only by only allowing creates. You could enable moderation of user-generated content by providing update and delete access to a particular set of users or roles.

Object-Level Access Control

Once you’ve locked down your schema and class-level permissions, it’s time to think about how data is accessed by your users. Object-level access control enables one user’s data to be kept separate from another’s, because sometimes different objects in a class need to be accessible by different people. For example, a user’s private personal data should be accessible only to them.

Parse also supports the notion of anonymous users for those apps that want to store and protect user-specific data without requiring explicit login.

When a user logs into an app, they initiate a session with Parse. Through this session they can add and modify their own data but are prevented from modifying other users’ data.

Access Control Lists

The easiest way to control who can access which data is through access control lists, commonly known as ACLs. The idea behind an ACL is that each object has a list of users and roles along with what permissions that user or role has. A user needs read permissions (or must belong to a role that has read permissions) in order to retrieve an object’s data, and a user needs write permissions (or must belong to a role that has write permissions) in order to update or delete that object.

Once you have a User, you can start using ACLs. Remember: Users can be created through traditional username/password sign up, through a third-party login system like Facebook or Twitter, or even by using Parse’s automatic anonymous users functionality. To set an ACL on the current user’s data to not be publicly readable, all you have to do is:

var user = ParseUser.CurrentUser;
user.ACL = new ParseACL(user);

Most apps should do this. If you store any sensitive user data, such as email addresses or phone numbers, you need to set an ACL like this so that the user’s private information isn’t visible to other users. If an object doesn’t have an ACL, it’s readable and writeable by everyone. The only exception is the _User class. We never allow users to write each other’s data, but they can read it by default. (If you as the developer need to update other _User objects, remember that your master key can provide the power to do this.)

To make it super easy to create user-private ACLs for every object, we have a way to set a default ACL that will be used for every new object you create:

// not available in the .NET SDK

If you want the user to have some data that is public and some that is private, it’s best to have two separate objects. You can add a pointer to the private data from the public one.

var privateData = new ParseObject("PrivateUserData");
privateData.ACL = new ParseACL(ParseUser.CurrentUser);
privateData["phoneNumber"] = "555-5309";

ParseUser.CurrentUser["privateData"] =  privateData;

Of course, you can set different read and write permissions on an object. For example, this is how you would create an ACL for a public post by a user, where anyone can read it:

var acl = new ParseACL();
acl.PublicReadAccess = true;
acl.SetRoleWriteAccess(ParseUser.CurrentUser.ObjectId, true);