Xamarin SDK

This guide provides instructions to integrate Authgear with a Xamarin app. Supported platforms include:
Android
iOS
Setup Application in Authgear
Signup for an Authgear Portal account in https://portal.authgearapps.com/. Or you can use your self-deployed Authgear.
From the Project listing, create a new Project or select an existing Project. After that, we will need to create an application in the project.
Portal
authgear.yaml (self-deployed)
Create an application
1.Go to Applications on the left menu bar.
2.Click ⊕Add Application in the top tool bar.
3.Input the name of your application, e.g. "MyAwesomeApp".
4.Under Authorized Redirect URIs, Click "⊕Add URI".
5.In your IDE (e.g. Visual Studio), define a custom URI scheme that the users will be redirected back to your app after they have authenticated with Authgear, e.g. com.myapp.example://host/path.[^1]
6.Head back to Authgear Portal, fill in the Redirect URI that you have defined in the previous steps.
7.Click "Save" in the top tool bar and keep the Client ID. You can also obtain it again from the Applications list later.
8.(Optional) Click "Edit" if you wish to configure more authentication settings.
If you wish to validate JSON Web Token (JWT) in your own application server, select "Issue JWT as access token".[^2] If you wish to forward authentication requests to Authgear Resolver Endpoint, leave this unchecked. See comparisons in Backend Integration.
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oauth:
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  clients:
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    - name: your_app_name
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      client_id: a_random_generated_string
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      redirect_uris:
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        - "com.myapp.example://host/path"
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      grant_types:
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        - authorization_code
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        - refresh_token
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      response_types:
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        - code
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        - none
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Create a Xamarin app
Open Visual Studio
Create a new project
Choose the Xamarin.Forms template
Install the SDK
Search for "Authgear.Xamarin" on nuget.org and add it to your base project.
https://www.nuget.org/packages/Authgear.Xamarin/​
Authgear.Xamarin targets MonoAndroid 12.0 on Android, and Xamarin.iOS10 on iOS. Update the target framework of the Android and iOS projects to match Authgear.Xamarin's target frameworks.
Update Android and iOS project's Xamarin.Essentials to 1.7.2.
Platform Integration
To finish the integration, setup the app to handle the redirectURI specified in the application. This part requires platform specific integration.
Android
Define your own callback activity
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using System;
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​
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using Android.App;
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using Android.Content.PM;
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using Android.Runtime;
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using Android.OS;
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using Authgear.Xamarin;
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using Xamarin.Forms;
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​
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namespace MyApp.Droid
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{
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    [Activity(NoHistory = true, LaunchMode = LaunchMode.SingleTop, Exported = true)]
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    [IntentFilter(new[] { Android.Content.Intent.ActionView },
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        Categories = new[] { Android.Content.Intent.CategoryDefault, Android.Content.Intent.CategoryBrowsable },
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        DataScheme = "com.myapp.example")]
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    public class WebAuthenticationCallbackActivity : Xamarin.Essentials.WebAuthenticatorCallbackActivity
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    {
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    }
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}
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Initialize a global AuthgearSdk instance
In your MainActivity.cs
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using System;
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​
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using Android.App;
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using Android.Content.PM;
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using Android.Runtime;
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using Android.OS;
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​
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using Xamarin.Forms;
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using Authgear.Xamarin;
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​
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namespace MyApp.Droid
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{
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    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
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    {
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        protected override void OnCreate(Bundle savedInstanceState)
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        {
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            // ...
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​
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            var authgear = new AuthgearSdk(this, new AuthgearOptions
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            {
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                ClientId = CLIENT_ID,
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                AuthgearEndpoint = ENDPOINT
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            });
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            DependencyService.RegisterSingleton<AuthgearSdk>(authgear);
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            LoadApplication(new App());
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​
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            // ...
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        }
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​
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        // other methods are omitted for brevity.
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    }
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}
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iOS
Add the following key-value pair in your iOS project Info.plist
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
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<plist version="1.0">
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<dict>
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        <!-- other entries ... -->
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        <key>CFBundleURLTypes</key>
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        <array>
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          <dict>
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            <key>CFBundleURLName</key>
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            <string>com.myapp.example://host/path</string>
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​
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            <key>CFBundleURLSchemes</key>
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            <array>
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              <string>com.myapp.example</string>
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            </array>
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​
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            <key>CFBundleTypeRole</key>
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            <string>Editor</string>
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          </dict>
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        </array>
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</dict>
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</plist>
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Initialize a global AuthgearSdk instance
In your AppDelegate.cs
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using Xamarin.Essentials;
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using Xamarin.Forms;
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using Authgear.Xamarin;
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​
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namespace MyApp.iOS
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{
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    [Register("AppDelegate")]
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    public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
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    {
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        public override bool FinishedLaunching(UIApplication app, NSDictionary options)
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        {
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            global::Xamarin.Forms.Forms.Init();
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            var authgear = new AuthgearSdk(app, new AuthgearOptions
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            {
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                ClientId = CLIENT_ID,
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                AuthgearEndpoint = ENDPOINT
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            });
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            DependencyService.RegisterSingleton<AuthgearSdk>(authgear);
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            LoadApplication(new App());
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​
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            return base.FinishedLaunching(app, options);
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        }
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​
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        public override bool OpenUrl(UIApplication app, NSUrl url, NSDictionary options)
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        {
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            return Xamarin.Essentials.Platform.OpenUrl(app, url, options);
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        }
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​
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        public override bool ContinueUserActivity(UIApplication application, NSUserActivity userActivity, UIApplicationRestorationHandler completionHandler)
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        {
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            if (Xamarin.Essentials.Platform.ContinueUserActivity(application, userActivity, completionHandler))
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                return true;
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            return base.ContinueUserActivity(application, userActivity, completionHandler);
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        }
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    }
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}
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Try authenticate
Edit your MainPage.xaml
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<?xml version="1.0" encoding="utf-8" ?>
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<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
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             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
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             x:Class="testauthgear.MainPage">
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​
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    <StackLayout>
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        <Frame BackgroundColor="#2196F3" Padding="24" CornerRadius="0">
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            <Label Text="Welcome to Xamarin.Forms!" HorizontalTextAlignment="Center" TextColor="White" FontSize="36"/>
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        </Frame>
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        <Button Text="Configure" Clicked="Configure_Clicked" />
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        <Button Text="Authenticate" Clicked="Authenticate_Clicked"/>
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    </StackLayout>
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​
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</ContentPage>
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Edit your MainPage.xaml.cs
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using System;
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using System.Collections.Generic;
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using System.ComponentModel;
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using System.Linq;
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using System.Text;
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using System.Threading.Tasks;
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using Xamarin.Forms;
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using Authgear.Xamarin;
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​
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namespace MyApp
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{
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    public partial class MainPage : ContentPage
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    {
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        private AuthgearSdk authgear;
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​
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​
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        public MainPage()
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        {
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            InitializeComponent();
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            authgear = DependencyService.Get<AuthgearSdk>();
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        }
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​
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        async void Configure_Clicked(object sender, EventArgs e)
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        {
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            // You must configure the instance before use.
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            // Typically you should do this once on app launch.
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            await authgear.ConfigureAsync();
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        }
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​
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        async void Authenticate_Clicked(object sender, EventArgs e)
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        {
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            var userInfo = await authgear.AuthenticateAsync(new AuthenticateOptions
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            {
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                RedirectUri = REDIRECT_URI
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            });
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        }
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    }
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}
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Get the Logged In State
The SessionState reflects the user logged in state in the SDK locally on the device. That means even the SessionState is Authenticated, the session may be invalid if it is revoked remotely. After initializing the Authgear SDK, call FetchUserInfoAsync to update the SessionState as soon as it is proper to do so.
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// value can be NoSession or Authenticated
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// After Authgear.ConfigureAsync, it only reflects local state.
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var sessionState = authgear.SessionState;
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​
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if (sessionState == SessionState.Authenticated)
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{
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    try
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    {
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        var userInfo = await authgear.FetchUserInfoAsync();
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        // sessionState is now up to date
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    }
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    catch (Exception ex)
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    {
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        // sessionState is now up to date
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        // it will change to NoSession if the session is invalid
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    }
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}
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Logout
To log out the user from the current app session, you need to invoke thelogoutfunction.
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await authgear.LogoutAsync();
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Calling An API
To include the access token to the HTTP requests to your application server, you set the bearer token manually by using authgear.AccessToken.
Using HttpClient
You can get the access token through authgear.AccessToken. Call RefreshAccessTokenIfNeededAsync every time before using the access token, the function will check and make the network call only if the access token has expired. Then, include the access token into the Authorization header of the http request.
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await authgear.RefreshAccessTokenIfNeededAsync();
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// Access token is ready to use
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// AccessToken can be string or undefined
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// It will be empty if user is not logged in or session is invalid
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var accessToken = authgear.AccessToken;
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var client = GetHttpClient();  // Get the re-used http client of your app, as per recommendation.
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var httpRequestMessage = new HttpRequestMessage(myHttpMethod, myUrl);
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httpRequestMessage.Headers.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);
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Next steps
To protect your application server from unauthorized access. You will need to integrate your backend with Authgear.
Backend Integration
Xamarin SDK Reference
For detailed documentation on the Xamarin SDK, visit Xamarin SDK Reference​
Footnote
[^1]: For futher instruction on setting up custom URI scheme in Xamarin, see https://www.xamarinhelp.com/uri-scheme/ [^2]: For more explaination on JWT, see https://en.wikipedia.org/wiki/JSON_Web_Token​