Authenticate Users - .NET SDK
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The SDK provides an API for authenticating users using any enabled
authentication provider. Instantiate a
Credentials
object and pass
it to the
LogInAsync()
method to authenticate and obtain a User
instance. The Credentials class exposes factory methods that correspond to
each of the authentication providers:
Before you can authenticate a user, ensure you have:
Enabled one or more authentication providers
Log In
Anonymous User
If you have enabled Anonymous authentication in the App Services UI, users can immediately log into your app without providing any identifying information. The following code shows how to do this:
var user = await app.LogInAsync(Credentials.Anonymous());
Email/Password User
If you have enabled Email/Password authentication, you can log in using the following code:
var user = await app.LogInAsync( Credentials.EmailPassword("caleb@example.com", "shhhItsASektrit!"));
API Key User
If you have enabled API Key authentication, you can log in using the following code:
var user = await app.LogInAsync(Credentials.ApiKey(apiKey));
Custom JWT User
If you have enabled the Custom JWT authentication provider, you can log in using the following code:
var user = await app.LogInAsync(Credentials.JWT(jwt_token));
Custom Function User
If you have enabled the Custom Function authentication provider, you can log in using the following code:
var functionParameters = new { username = "caleb", password = "shhhItsASektrit!", IQ = 42, isCool = false }; var user = await app.LogInAsync(Credentials.Function(functionParameters));
Facebook User
The Facebook authentication provider allows you to authenticate users through a Facebook app using their existing Facebook account.
Important
Enable the Facebook Auth Provider
To log a user in with their existing Facebook account, you must configure and enable the Facebook authentication provider for your application.
Important
Do Not Store Facebook Profile Picture URLs
Facebook profile picture URLs include the user's access token to grant permission to the image. To ensure security, do not store a URL that includes a user's access token. Instead, access the URL directly from the user's metadata fields when you need to fetch the image.
var user = await app.LogInAsync(Credentials.Facebook(facebookToken));
Google User
If you have enabled Google authentication, you can log in using the following code:
var user = await app.LogInAsync(Credentials.Google(googleAuthCode, GoogleCredentialType.AuthCode));
Apple User
If you have enabled Sign-in with Apple authentication, you can log in using the following code:
var user = await app.LogInAsync(Credentials.Apple(appleToken));
Tip
If you get a Login failed error saying that the token contains
an invalid number of segments, verify that you're passing a UTF-8-encoded
string version of the JWT.
Offline Login
When your Realm application authenticates a user, it caches the user's credentials. You can check for existing user credentials to bypass the login flow and access the cached user. Use this to open a realm offline.
Note
Initial login requires a network connection
When a user signs up for your app, or logs in for the first time with an existing account on a client, the client must have a network connection. Checking for cached user credentials lets you open a realm offline, but only if the user has previously logged in while online.
The following example checks if there is a cached User object. If not, it logs the user in. Otherwise, it uses the cached credentials:
if (app.CurrentUser == null) { // App must be online for user to authenticate user = await app.LogInAsync( Credentials.EmailPassword("caleb@mongodb.com", "shhhItsASektrit!")); config = new PartitionSyncConfiguration("_part", user); realm = await Realm.GetInstanceAsync(config); } else { // This works whether online or offline user = app.CurrentUser; config = new PartitionSyncConfiguration("_part", user); realm = Realm.GetInstance(config); }
Log a User Out
Once logged in, you can log out by calling the LogOutAsync() method:
await user.LogOutAsync();
Warning
When a user logs out, you can no longer read or write data in any synced realms that the user opened. As a result, any operation that has not yet completed before the initiating user logs out cannot complete successfully and will likely result in an error. Any data in a write operation that fails in this way will be lost.
Retrieve the Current User
Once you have an authenticated user, you can retrieve the User object with the
App.CurrentUser
property. The CurrentUser object is persisted in local storage, so even if
the app shuts down after the initial authentication, you do not need to call
LoginAsync again (unless the user logged out). Instead, use
Realm.GetInstance(config),
where config is a PartitionSyncConfiguration
object. This approach results in a faster start-up and also enables the user to
work offline.
Get a User Access Token
When a user logs in, Atlas App Services creates an access token for the user that grants them access to your App. The Realm SDK automatically manages access tokens, refreshes them when they expire, and includes a valid access token for the current user with each request. If you send requests outside of the SDK (for example, through the GraphQL API) then you need to include the user's access token with each request, and manually refresh the token when it expires.
You can access and refresh a logged in user's access token in the SDK from their
Realm.User object, as in the following example:
// Returns a valid user access token to authenticate requests public async Task<string> GetValidAccessToken(User user) { // An already logged in user's access token might be stale. To // guarantee that the token is valid, refresh it. await user.RefreshCustomDataAsync(); return user.AccessToken; }