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This tutorial demonstrates how to add user login to a Xamarin application using Auth0. We recommend you to Log in to follow this quickstart with examples configured for your account.

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System requirements: Visual Studio 2017 or Visual Studio for Mac | Xamarin for Visual Studio 4.5 | Auth0.OidcClient.Android 1.0.0 | Auth0.OidcClient.iOS 1.0.0

New to Auth? Learn How Auth0 works, how it integrates with Native Applications and which protocol it uses.

Configure Auth0

Get Your Application Keys

When you signed up for Auth0, a new application was created for you, or you could have created a new one.

Your will need some details about that application to communicate with Auth0. You can get these details from the Application Settings section in the Auth0 dashboard.

You need the following information:

  • Client ID
  • Domain

If you download the sample from the top of this page these details are filled out for you.

If you have more than one application in your account, the sample comes with the values for your Default App.

App Dashboard

Configure Callback URLs

A callback URL is a URL in your application where Auth0 redirects the user after they have authenticated.

You need to whitelist the callback URL for your app in the Allowed Callback URLs field in your Application Settings. If you do not set any callback URL, your users will see a mismatch error when they log in.

Callback URLs are the URLs that Auth0 invokes after the authentication process. Auth0 routes your application back to this URL and appends additional parameters to it, including an access code which will be exchanged for an ID Token, Access Token, and Refresh Token.

Since callback URLs can be manipulated, you will need to add your application's URL to your application's Allowed Callback URLs for security. This will enable Auth0 to recognize these URLs as valid. If omitted, authentication will not be successful.

  • For Android, the callback URL will be in the format

    YOUR_ANDROID_PACKAGE_NAME://YOUR_AUTH0_DOMAIN/android/YOUR_ANDROID_PACKAGE_NAME/callback
    

    where YOUR_ANDROID_PACKAGE_NAME is the Package Name for your application, such as com.mycompany.myapplication.

  • For iOS, the callback URL will be in the format

    YOUR_BUNDLE_IDENTIFIER://YOUR_AUTH0_DOMAIN/ios/YOUR_BUNDLE_IDENTIFIER/callback
    

    where YOUR_BUNDLE_IDENTIFIER is the Bundle Identifier for your application, such as com.mycompany.myapplication.

Ensure that the Callback URL is in lowercase.

Install Dependencies

If you are using Visual Studio 2017, simply open the Package Manager Console (View -> Other Windows -> Package Manager Console), and install the package:

For Android:

Install-Package Auth0.OidcClient.Android

For iOS:

Install-Package Auth0.OidcClient.iOS

Alternatively, if you are using Visual Studio for Mac, please perform the following steps:

  1. With the project loaded in Visual Studio for Mac, Ctrl+click (or right click) on the Packages folder of the project in the Solution Pad, and select Add Packages...
  2. The Add Packages dialog will appear. Search and locate the package called Auth0.OidcClient.Android or Auth0.OidcClient.iOS depending on your platform.
  3. Tick the checkbox next to the package to select it, and click the Add Package button

Trigger Authentication

To integrate Auth0 login into your application, instantiate an instance of the Auth0Client class, configuring the Auth0 Domain and Client ID:

using Auth0.OidcClient;

var client = new Auth0Client(new Auth0ClientOptions
{
    Domain = "YOUR_AUTH0_DOMAIN",
    ClientId = "YOUR_CLIENT_ID"
});

Then, call the LoginAsync method which will redirect the user to the login screen. You will typically do this in the event handler for a UI control such as a Login button.

var loginResult = await client.LoginAsync();

Handing the callback URL

After a user has logged in, they will be redirected back to your application at the Callback URL that was registered before. In both Android and iOS you need to handle this callback to complete the authentication flow.

Android

Register an intent which will handle this callback URL. An easy way to do this is to register the intent on the same activity from which you called the LoginAsync method to initiate the authentication flow.

[Activity(Label = "AndroidSample", MainLauncher = true, Icon = "@drawable/icon",
    LaunchMode = LaunchMode.SingleTask)]
[IntentFilter(
    new[] { Intent.ActionView },
    Categories = new[] { Intent.CategoryDefault, Intent.CategoryBrowsable },
    DataScheme = "YOUR_ANDROID_PACKAGE_NAME",
    DataHost = "YOUR_AUTH0_DOMAIN",
    DataPathPrefix = "/android/YOUR_ANDROID_PACKAGE_NAME/callback")]
public class MainActivity : Activity
{
    // Code omitted
}

Replace YOUR_ANDROID_PACKAGE_NAME in the code sample above with the actual Package Name for your application, such as com.mycompany.myapplication. Also ensure that all the text for the DataScheme, DataHost, and DataPathPrefix is in lower case. Also, set LaunchMode = LaunchMode.SingleTask for the Activity, otherwise the system will create a new instance of the activity every time the Callback URL gets called.

Now write code to handle the intent. You can do this by overriding the OnNewIntent method. Inside the method you need to call the Send method on the ActivityMediator to complete the authentication cycle:

protected override async void OnNewIntent(Intent intent)
{
    base.OnNewIntent(intent);

    Auth0.OidcClient.ActivityMediator.Instance.Send(intent.DataString);
}

iOS

Register the URL scheme for your Callback URL which your application should handle:

  1. Open your application's Info.plist file in Visual Studio for Mac, and go to the Advanced tab.
  2. Under URL Types, click the Add URL Type button
  3. Set the Identifier as Auth0, the URL Schemes the same as your application's Bundle Identifier, and the Role as None

This is an example of the XML representation of your info.plist file after you have added the URL Type:

<key>CFBundleURLTypes</key>
<array>
    <dict>
        <key>CFBundleTypeRole</key>
        <string>None</string>
        <key>CFBundleURLName</key>
        <string>Auth0</string>
        <key>CFBundleURLSchemes</key>
        <array>
            <string>YOUR_BUNDLE_IDENTIFIER</string>
        </array>
    </dict>
</array>

You need to handle the Callback URL in the OpenUrl event in your AppDelegate class. You need to notify the Auth0 OIDC Client to finish the authentication flow by calling the Send method of the ActivityMediator singleton, pass along the URL that was sent in:

using Auth0.OidcClient;

[Register("AppDelegate")]
public class AppDelegate : UIApplicationDelegate
{
    public override bool OpenUrl(UIApplication application, NSUrl url, string sourceApplication, NSObject annotation)
    {
        ActivityMediator.Instance.Send(url.AbsoluteString);

        return true;
    }
}

Run the application

With the above code in place, a user can log in to your application using Auth0.

Lock UI

Accessing the User's Information

The returned login result will indicate whether authentication was successful and if so contain the tokens and claims of the user.

Authentication Error

You can check the IsError property of the result to see whether the login has failed. The ErrorMessage will contain more information regarding the error which occurred.

// For Android
var loginResult = await client.ProcessResponseAsync(intent.DataString, authorizeState);

// For iOS
var loginResult = await client.LoginAsync();

if (loginResult.IsError)
{
    Debug.WriteLine($"An error occurred during login: {loginResult.Error}")
}

Accessing the tokens

On successful login, the login result will contain the ID Token and Access Token in the IdentityToken and AccessToken properties respectively.

var loginResult = await client.ProcessResponseAsync(intent.DataString, authorizeState);

if (!loginResult.IsError)
{
    Debug.WriteLine($"id_token: {loginResult.IdentityToken}");
    Debug.WriteLine($"access_token: {loginResult.AccessToken}");
}

Obtaining the User Information

On successful login, the login result will contain the user information in the User property, which is a ClaimsPrincipal.

To obtain information about the user, you can query the claims. You can, for example, obtain the user's name and email address from the name and email claims:

if (!loginResult.IsError)
{
    Debug.WriteLine($"name: {loginResult.User.FindFirst(c => c.Type == "name")?.Value}");
    Debug.WriteLine($"email: {loginResult.User.FindFirst(c => c.Type == "email")?.Value}");
}

The exact claims returned will depend on the scopes that were requested. For more information see the Using Scopes in the Auth0 OIDC Application documentation.

You can obtain a list of all the claims contained in the ID Token by iterating through the Claims collection:

if (!loginResult.IsError)
{
    foreach (var claim in loginResult.User.Claims)
    {
        Debug.WriteLine($"{claim.Type} = {claim.Value}");
    }
}
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