auth0-net-android Integration

Add Auth0 authentication to .NET Android applications. This skill integrates the Auth0.OidcClient.AndroidX NuGet package which uses Chrome Custom Tabs for secure OIDC-based login and logout flows with PKCE.

Agent instruction: Before providing SDK setup instructions, fetch the latest release version by running:

gh api repos/auth0/auth0-oidc-client-net/releases --jq '[.[] | select(.tag_name | startswith("androidx-")) | .tag_name | ltrimstr("androidx-")] | .[0]'

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Use the returned version in all dependency lines instead of any hardcoded version below.

Prerequisites

• .NET 8.0 SDK or later
• Visual Studio 2022 (17.8+) with .NET Android workload, or JetBrains Rider
• Android SDK API 21+ (minimum), API 34+ recommended for net9.0-android
• Auth0 account with a Native application configured
• Node.js 20+ (for Auth0 CLI automated setup)

When NOT to Use

Quick Start Workflow

Agent instruction: Before starting, examine the user's project:

1. Identify the .NET version from the .csproj file (TargetFramework)
2. Check for existing authentication implementations — search for existing login/logout handlers and hook into them if found (reuse existing UI elements like login buttons rather than creating duplicates)
3. Note the project's namespace and package name from the .csproj or AndroidManifest.xml
4. Look for existing Auth0Client or Auth0ClientOptions usage to avoid duplicate configuration

1. Install SDK: dotnet add package Auth0.OidcClient.AndroidX
2. Configure Auth0: See Setup Guide for automatic or manual configuration.
3. Integrate authentication: Add Auth0Client instantiation, configure the IntentFilter on your Activity, and wire login/logout to UI actions.
4. Handle callback: Override OnNewIntent and call ActivityMediator.Instance.Send(intent.DataString) to complete the authentication flow.
5. Build and verify: dotnet build

Agent instruction: When writing the Auth0Client configuration:

• Pass this (the Activity) as the second argument to Auth0Client constructor.
• Always set Scope = "openid profile email offline_access" — the offline_access scope is required to receive refresh tokens, enabling silent token renewal without re-prompting the user.
• The callback URL format is YOUR_ANDROID_PACKAGE_NAME://YOUR_AUTH0_DOMAIN/android/YOUR_ANDROID_PACKAGE_NAME/callback — all lowercase.
• The DataScheme in the IntentFilter must be lowercase or Android will not receive callbacks.
• Set LaunchMode = LaunchMode.SingleTask on the Activity to prevent duplicate instances. Do NOT use SingleTop — it does not correctly handle the callback redirect and will create duplicate Activity instances.
• The Activity should either extend Auth0ClientActivity OR manually override OnNewIntent and call ActivityMediator.Instance.Send(intent.DataString).
• Store tokens securely: After successful login, persist AccessToken and RefreshToken using SecureStorage (MAUI/Essentials) or EncryptedSharedPreferences (AndroidX Security — requires dotnet add package Xamarin.AndroidX.Security.SecurityCrypto). Never store tokens in plain SharedPreferences or in-memory variables only.

After writing configuration and code, verify the build succeeds:

dotnet build

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If the build fails, attempt to fix the issue. After 5-6 failed attempts, ask the user for help.

WebAuth — How Authentication Works

The SDK uses the WebAuth pattern via Chrome Custom Tabs (the system browser). When LoginAsync() is called, the SDK:

1. Constructs the /authorize URL with PKCE parameters
2. Opens Chrome Custom Tabs with the authorization URL
3. After authentication, Auth0 redirects to the native callback URL
4. The Android system matches the URL scheme and delivers it to your Activity via OnNewIntent
5. ActivityMediator completes the token exchange

This is the standard OAuth 2.0 Authorization Code flow with PKCE, recommended for native mobile applications.

Callback URL Configuration

The native callback URL for .NET Android uses the package name as the scheme. The format is:

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 example: com.mycompany.myapp://tenant.us.auth0.com/android/com.mycompany.myapp/callback.

Note: Some Auth0 native SDKs use https://{domain}/android/{package}/callback as the callback URL format. The .NET Android SDK uses the package name as the URL scheme instead.

Ensure that the Callback URL is in lowercase.

This URL must be:

1. Registered in Auth0 Dashboard under Allowed Callback URLs and Allowed Logout URLs
2. Matched by the IntentFilter attributes (DataScheme, DataHost, DataPathPrefix) on your Activity

Done When

• Auth0.OidcClient.AndroidX package installed (latest stable version)
• Auth0Client configured with Domain, ClientId, and Scope = "openid profile email offline_access"
• IntentFilter configured on Activity with correct DataScheme, DataHost, DataPathPrefix
• LaunchMode = LaunchMode.SingleTask set on Activity
• OnNewIntent handled with ActivityMediator.Instance.Send(intent.DataString)
• Callback URL added to Auth0 Dashboard Allowed Callback URLs and Allowed Logout URLs
• Tokens stored securely (SecureStorage or EncryptedSharedPreferences)
• Login/logout flow working
• Build succeeds with no errors

Detailed Documentation

• Setup Guide — Auth0 tenant configuration, SDK installation, IntentFilter setup
• Integration Patterns — Login/logout flows, token access, user profile, error handling
• API Reference & Testing — Full Auth0ClientOptions reference, claims, testing checklist, troubleshooting

Common Mistakes

Testing Notes

Agent instruction: Remind the user to test on a physical device in addition to emulators. Some WebAuth behaviors (Chrome Custom Tabs, URL scheme interception) may differ on physical devices vs. emulators. Test the full login → callback → token flow on real hardware before shipping.

Physical Device Testing:

• Login flow: Chrome Custom Tab opens → authenticate → returns to app
• Callback: OnNewIntent fires with correct intent data
• Logout flow: Browser opens → session cleared → returns to app
• Cancel: User presses back → app handles UserCancel gracefully

Related Skills

• auth0-maui — .NET MAUI cross-platform apps (iOS + Android + Windows)
• auth0-net-ios — .NET iOS-only apps
• auth0-android — Android-native Kotlin apps
• auth0-aspnetcore-authentication — ASP.NET Core server-side web apps
• auth0-aspnetcore-api — ASP.NET Core Web API with JWT validation

Quick Reference

using Auth0.OidcClient;

var client = new Auth0Client(new Auth0ClientOptions
{
    Domain = "YOUR_AUTH0_DOMAIN",
    ClientId = "YOUR_AUTH0_CLIENT_ID",
    Scope = "openid profile email offline_access"
}, this);

Login

var loginResult = await client.LoginAsync();

Handle Errors

var loginResult = await client.LoginAsync();

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

Access Tokens

var loginResult = await client.LoginAsync();

if (!loginResult.IsError)
{
    Debug.WriteLine($"Authentication successful.");
}

User Information

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}");
}

List All Claims

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

Logout

BrowserResultType browserResult = await client.LogoutAsync();

Activity with IntentFilter (Required)

[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
}

Handle Callback in OnNewIntent (Required)

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

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

References

• .NET Android & iOS Quickstart
• GitHub Repository
• NuGet Package — Auth0.OidcClient.AndroidX
• SDK API Documentation