Authenticate Users - .NET SDK

Log In

var user = await app.LogInAsync(Credentials.Anonymous());

var user = await app.LogInAsync(
    Credentials.EmailPassword("caleb@mongodb.com", "MySekritPwd"));

var user = await app.LogInAsync(Credentials.ApiKey(apiKey));

var user =
    await app.LogInAsync(Credentials.JWT(jwt_token));

var functionParameters = new
{
    username = "caleb",
    password = "MySekritPwd",
    IQ = 42,
    hasPets = true
};
var user =
    await app.LogInAsync(Credentials.Function(functionParameters));

var user =
    await app.LogInAsync(Credentials.Facebook(facebookToken));

var user =
    await app.LogInAsync(Credentials.Google(googleAuthCode, GoogleCredentialType.AuthCode));

var user =
    await app.LogInAsync(Credentials.Apple(appleToken));

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.

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", "MySekritPwd"));
    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();

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.

// 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;
}

Refresh Token Expiration

Refresh tokens expire after a set period of time. When the refresh token expires, the access token can no longer be refreshed and the user must log in again.

If the refresh token expires after the realm is open, the device will not be able to sync until the user logs in again. Your sync error handler should implement logic that catches a token expired error when attempting to sync, then redirect users to a login flow.

For information on configuring refresh token expiration, refer to Manage User Sessions in the App Services documentation.

Observe Authentication Changes

You can observe a flow of authentication change events by calling User.Changed() on a valid user object.

Currently, User.Changed() triggers on all user events and you should add a handler to ensure your responses to events are idempotent.

app.CurrentUser.Changed += (change, _) =>
{
    Debug.WriteLine($"Auth change: {change}, {_}");
};