Access services with OAuth 2.0 (.NET MAUI)

Learn how to authenticate a user to access a secure ArcGIS service with OAuth 2.0.

In this tutorial, you will build an app that uses named user login credentials to access a secure ArcGIS service using OAuth 2.0.

You can use different types of authentication to access ArcGIS location services. To implement OAuth 2.0, you can use your ArcGIS account to register an application and get a client ID, and then configure your app to redirect users to login with their credentials when the service or content is accessed. This is known as user authentication. If the app uses premium services that consume credits, the app user's account will be charged.

You will implement OAuth 2.0 so users can sign in to ArcGIS to access the ArcGIS World Traffic service.

Prerequisites

Steps

Configure OAuth 2.0 for your app

Use the ArcGIS Developer dashboard to create an application, generate a client ID, and define a redirect URL to access secure services.

1. Sign in to your ArcGIS developer account. If you don't already have one, sign-up for free. You need to sign in so you can create an application and get a client ID for authentication.
2. Click the OAuth 2.0 tab in the ribbon at the top.
3. Click the New Application button in the upper-left of the page.
4. In the Create New Application window, provide a Name and an optional Description for your application definition. Then click Create application. When the application is created, Client ID, Client Secret, and Temporary Token values will also be generated.
5. Click the Add URI button at the bottom of the page to add a redirect URL.
6. In the Add Allowed URI window, type my-app://auth and click Add URI.

Open a Visual Studio solution

1. To start the tutorial, complete the Display a map (.NET MAUI) tutorial or download and unzip the solution.

2. Open the .sln file in Visual Studio.

3. If you downloaded the solution project, set your API key.

   Instructions for setting the API key

   An API Key enables access to services, web maps, and web scenes hosted in ArcGIS Online.

   If necessary, set the  API Key.

   1. Go to your developer dashboard to get your API key. For these tutorials, use your default API key. It is scoped to include all of the services demonstrated in the tutorials.

   2. In the Solution Explorer, open MauiProgram.cs by double-clicking.

   3. Use the existing builder variable in the CreateMauiApp() function to call UseArcGISRuntime(). Use a lambda function to call UseApiKey() on a config parameter to set the ApiKey property on ArcGISRuntimeEnvironment.

      MauiProgram.cs

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      public static class MauiProgram
      {
          public static MauiApp CreateMauiApp()
      	{
      		var builder = MauiApp.CreateBuilder();
      		builder
      			.UseMauiApp<App>()
      			.ConfigureFonts(fonts =>
      			{
      				fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");
      				fonts.AddFont("OpenSans-Semibold.ttf", "OpenSansSemibold");
                  });
      
      		builder.UseArcGISRuntime(config => config.UseApiKey("YOUR_API_KEY"));
      
      #if DEBUG
              builder.Logging.AddDebug();
      #endif
      
      		return builder.Build();
      	}
      }

   4. Save and close the MauiProgram.cs file.

Update the tutorial name used in the project (optional)

The Visual Studio solution, project, and the namespace for all classes currently use the name DisplayAMap. Follow the steps below if you prefer the name to reflect the current tutorial. These steps are not required, your code will still work if you keep the original name.

Add a reference to WinUIEx

1. In the Visual Studio > Solution Explorer, right-click the project node and choose Edit project file.

2. Include the following package reference in the AccessServicesWithOAuth.csproj file.

   AccessServicesWithOAuth.csproj

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   	<!-- WinUIEx is used to workaround the lack of a WebAuthenticationBroker for WinUI. https://github.com/microsoft/WindowsAppSDK/issues/441 -->
   
   	<ItemGroup Condition="'$(TargetFramework)' == 'net8.0-windows10.0.19041.0'">
     		<PackageReference Include="WinUIEx" Version="1.8.0" />
   	</ItemGroup>
   

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3. Save and close the project file.

Platform-specific setup for WebAuthenticator functionality

The .NET MAUI WebAuthenticator helps you implement browser-based authentication flows, which listen for a callback to a specific URL registered to the app. To use the .NET MAUI WebAuthenticator some platform-specific setup is required.

Windows

For WinUI 3, the callback URI protocol needs to be included in the Package.appxmanifest file. The Protocol Name must match the URI scheme of the redirect URL on your ArcGIS developer account.

1. In the Visual Studio > Solution Explorer, navigate to the Platforms\Windows folder.

2. Open the Package.appxmanifest file in an XML (text) editor and add the following lines.

   Package.appxmanifest

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     <Applications>
       <Application Id="App" Executable="$targetnametoken$.exe" EntryPoint="$targetentrypoint$">
         <uap:VisualElements
           DisplayName="$placeholder$"
           Description="$placeholder$"
           Square150x150Logo="$placeholder$.png"
           Square44x44Logo="$placeholder$.png"
           BackgroundColor="transparent">
           <uap:DefaultTile Square71x71Logo="$placeholder$.png" Wide310x150Logo="$placeholder$.png" Square310x310Logo="$placeholder$.png" />
           <uap:SplashScreen Image="$placeholder$.png" />
         </uap:VisualElements>
   
         <Extensions>
           <uap:Extension Category="windows.protocol">
             <uap:Protocol Name="my-app"/>
           </uap:Extension>
         </Extensions>
   
       </Application>
     </Applications>
   

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iOS and Mac Catalyst

The iOS and Mac Catalyst platforms require the inclusion of your app's callback URI pattern in their Info.plist files. The CFBundleURLSchemes value must match the URI scheme of the redirect URL on your ArcGIS developer account.

1. In the Visual Studio > Solution Explorer, navigate to the Platforms\iOS folder.

2. Open the Info.plist file in an XML (text) editor and add the following lines. Make the same edits in the Platforms\MacCatalyst\Info.plist file.

   Info.plist

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   	<key>XSAppIconAssets</key>
   	<string>Assets.xcassets/appicon.appiconset</string>
   
      <key>CFBundleURLTypes</key>
      <array>
         <dict>
            <key>CFBundleURLName</key>
            <string>My App</string>
            <key>CFBundleURLSchemes</key>
            <array>
                  <string>my-app</string>
            </array>
            <key>CFBundleTypeRole</key>
            <string>Editor</string>
         </dict>
      </array>
   

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Android

For Android, the AndroidManifest.xml file must be updated to include the CustomTabsService, which is required by the WebAuthenticator.

1. In the Visual Studio > Solution Explorer, navigate to the Platforms\Android folder.

2. Open the AndroidManifest.xml file in an XML (text) editor and add the following lines.

   AndroidManifest.xml

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   	<!--https://github.com/dotnet/maui/issues/3760#issuecomment-1046241094-->
   
   	<queries>
   		<intent>
   			<action android:name="android.support.customtabs.action.CustomTabsService" />
   		</intent>
   	</queries>
   

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   Android also requires the implementation of WebAuthenticatorCallbackActivity class. This is included in the AuthenticationHelper.cs class covered in more detail later in this tutorial.

   More info

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               [Activity(NoHistory = true, Exported = true, LaunchMode = LaunchMode.SingleTop)]
               [IntentFilter(new[] { Intent.ActionView },
                  Categories = new[] { Intent.CategoryDefault, Intent.CategoryBrowsable },
                  DataScheme = "my-app", DataHost = "auth")]
               public class WebAuthenticationCallbackActivity : WebAuthenticatorCallbackActivity
               {
               }
   

   The Microsoft documentation covers getting started with the .NET MAUI WebAuthenticator in more detail.

Add a traffic layer

You will add a layer to display the ArcGIS World Traffic service, a dynamic map service that presents historical and near real-time traffic information for different regions in the world. This is a secure service and requires an ArcGIS Online organizational subscription.

1. In the Visual Studio > Solution Explorer, double-click MapViewModel.cs to open the file.

   More info

   The project uses the Model-View-ViewModel (MVVM) design pattern to separate the application logic (view model) from the user interface (view). MapViewModel.cs contains the view model class for the application, called MapViewModel. See the Microsoft documentation for more information about the Model-View-ViewModel pattern.

2. In the SetupMap() function, update the line that sets the Map property for the view model to instead store the map in a variable. Also change the line that sets the map's initial extent to use the variable.

   MapViewModel.cs

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           private void SetupMap()
           {
   
               // Create a new map with a 'topographic vector' basemap.
               var trafficMap = new Map(BasemapStyle.ArcGISTopographic);
   
               var mapCenterPoint = new MapPoint(-118.805, 34.027, SpatialReferences.Wgs84);
   
               trafficMap.InitialViewpoint = new Viewpoint(mapCenterPoint, 100000);
   
           }
   

3. Create an ArcGISMapImageLayer to display the traffic service and add it to the map's collection of data layers (operational layers).

   MapViewModel.cs

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           private void SetupMap()
           {
   
               // Create a new map with a 'topographic vector' basemap.
               var trafficMap = new Map(BasemapStyle.ArcGISTopographic);
   
               var mapCenterPoint = new MapPoint(-118.805, 34.027, SpatialReferences.Wgs84);
   
               trafficMap.InitialViewpoint = new Viewpoint(mapCenterPoint, 100000);
   
               // Create a layer to display the ArcGIS World Traffic service.
               var trafficServiceUrl = "https://traffic.arcgis.com/arcgis/rest/services/World/Traffic/MapServer";
               var trafficLayer = new ArcGISMapImageLayer(new Uri(trafficServiceUrl));
   
               // Add the traffic layer to the map's data layer collection.
               trafficMap.OperationalLayers.Add(trafficLayer);
   
           }
   

4. Set the view model's Map property. Data binding handles displaying the map in the view.

   MapViewModel.cs

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           private void SetupMap()
           {
   
               // Create a new map with a 'topographic vector' basemap.
               var trafficMap = new Map(BasemapStyle.ArcGISTopographic);
   
               var mapCenterPoint = new MapPoint(-118.805, 34.027, SpatialReferences.Wgs84);
   
               trafficMap.InitialViewpoint = new Viewpoint(mapCenterPoint, 100000);
   
               // Create a layer to display the ArcGIS World Traffic service.
               var trafficServiceUrl = "https://traffic.arcgis.com/arcgis/rest/services/World/Traffic/MapServer";
               var trafficLayer = new ArcGISMapImageLayer(new Uri(trafficServiceUrl));
   
               // Add the traffic layer to the map's data layer collection.
               trafficMap.OperationalLayers.Add(trafficLayer);
   
               // Set the view model Map property with the new map.
               this.Map = trafficMap;
   
           }
   

5. Click Debug > Start Debugging (or press <F5> on the keyboard) to run the app.

You should see a map with the topographic basemap layer centered on the Santa Monica Mountains in California. The traffic layer doesn't appear because it requires authentication with ArcGIS Online.

Handle layer load errors

If a map attempts to load a layer based on a secured service without the required authentication, the layer is not added to the map. No exception is raised and unless you handle it in your code, the user may never know that the secured resource is missing from the map.

You will handle load status change events for the traffic layer and report an error message if the layer fails to load.

1. In the SetupMap() function, after the line that creates the traffic layer, add the following line of code to handle the layer's load status changed event. You will create the code for this handler in another step.

   MapViewModel.cs

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           private void SetupMap()
           {
   
               // Create a new map with a 'topographic vector' basemap.
               var trafficMap = new Map(BasemapStyle.ArcGISTopographic);
   
               var mapCenterPoint = new MapPoint(-118.805, 34.027, SpatialReferences.Wgs84);
   
               trafficMap.InitialViewpoint = new Viewpoint(mapCenterPoint, 100000);
   
               // Create a layer to display the ArcGIS World Traffic service.
               var trafficServiceUrl = "https://traffic.arcgis.com/arcgis/rest/services/World/Traffic/MapServer";
               var trafficLayer = new ArcGISMapImageLayer(new Uri(trafficServiceUrl));
   
               // Handle changes in the traffic layer's load status to check for errors.
               trafficLayer.LoadStatusChanged += TrafficLayer_LoadStatusChanged;
   
               // Add the traffic layer to the map's data layer collection.
               trafficMap.OperationalLayers.Add(trafficLayer);
   
               // Set the view model Map property with the new map.
               this.Map = trafficMap;
   
           }
   

2. Below the SetupMap() function, create the function that handles load status change events for the layer. If the layer fails to load, display an error message to the user.

   MapViewModel.cs

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           private async void TrafficLayer_LoadStatusChanged(object sender, Esri.ArcGISRuntime.LoadStatusEventArgs e)
   
           {
               // Report the error message if the traffic layer fails to load.
               if (e.Status == Esri.ArcGISRuntime.LoadStatus.FailedToLoad)
               {
                   var trafficLayer = sender as ArcGISMapImageLayer;
                   await MainThread.InvokeOnMainThreadAsync(() =>
                   {
                       Application.Current.MainPage.DisplayAlert("Traffic layer did not load", trafficLayer?.LoadError?.Message, "Ok");
                   });
               }
           }
   

3. Click Debug > Start Debugging (or press <F5> on the keyboard) to run the app.

You should see the same map display, but this time a message box reports a "Token required" error when the traffic layer fails to load. An access token is an authorization string that provides secure access to content, data, and functionality in ArcGIS location services. To load the traffic service layer, you will use OAuth to get an access token based on ArcGIS Online credentials.

Implement OAuth 2.0 authentication

This API abstracts some of the details for OAuth 2.0 authentication in your app. You can use classes such as AuthenticationManager to request, store, and manage credentials for secure resources.

You will add an authentication helper class that uses AuthenticationManager and encapsulates additional authentication logic.

1. From the Visual Studio Project menu, choose Add class .... Name the class AuthenticationHelper.cs then click Add. The new class is added to your project and opens in Visual Studio.

2. Select all the code in the class and delete it.

3. Copy all of the code below and paste it into the AuthenticationHelper.cs class in your project.

   AuthenticationHelper.cs

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   //   Copyright 2023 Esri
   //   Licensed under the Apache License, Version 2.0 (the "License");
   //   you may not use this file except in compliance with the License.
   //   You may obtain a copy of the License at
   //
   //   https://www.apache.org/licenses/LICENSE-2.0
   //
   //   Unless required by applicable law or agreed to in writing, software
   //   distributed under the License is distributed on an "AS IS" BASIS,
   //   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   //   See the License for the specific language governing permissions and
   //   limitations under the License.
   
   #if ANDROID
   
   using Android.App;
   using Application = Microsoft.Maui.Controls.Application;
   using Android.Content;
   using Android.Content.PM;
   
   #endif
   
   using Esri.ArcGISRuntime.Security;
   using System;
   using System.Collections.Generic;
   using System.Diagnostics;
   using System.Threading.Tasks;
   
   namespace AccessServicesWithOAuth
   {
   
       // A helper class that manages authenticating with a server to access secure resources.
       internal static class AuthenticationHelper
       {
           // Specify the client ID and redirect URL to use for OAuth authentication.
           // Create your OAuth application metadata using the ArcGIS developer dashboard:
           // https://developers.arcgis.com/dashboard/
   
           private const string OAuthClientID = "YOUR_CLIENT_ID";
           private const string OAuthRedirectUrl = "YOUR_REDIRECT_URL";
   
           static AuthenticationHelper()
           {
               // Use the OAuthAuthorize class (defined below) to show the login UI.
               AuthenticationManager.Current.OAuthAuthorizeHandler = new OAuthAuthorize();
   
               // Create a new ChallengeHandler that uses a method in this class to challenge for credentials.
               AuthenticationManager.Current.ChallengeHandler = new ChallengeHandler(PromptCredentialAsync);
           }
   
           // A function to register a secure server with the AuthenticationManager.
           // Pass in the URL of the server containing secure resources and, optionally, a client ID and
           // redirect URL (if not specified, the values defined above are used).
           public static void RegisterSecureServer(string url,
                                                   string clientID = OAuthClientID,
                                                   string redirectUrl = OAuthRedirectUrl)
           {
               // Define the server URL, authentication type, client ID, and redirect URL.
               ServerInfo portalServerInfo = new ServerInfo(new Uri(url))
               {
                   TokenAuthenticationType = TokenAuthenticationType.OAuthAuthorizationCode,
                   OAuthClientInfo = new OAuthClientInfo(clientID, new Uri(redirectUrl))
               };
   
               // Register the server information with the AuthenticationManager.
               AuthenticationManager.Current.RegisterServer(portalServerInfo);
           }
   
           // A function that adds a credential to AuthenticationManager based on a temporary token.
           // This is useful for testing an app with secured services without having to log in.
           public static void ApplyTemporaryToken(string url, string token)
           {
               // Create a new OAuth credential for the specified URL with the token.
               OAuthTokenCredential tempToken = new OAuthTokenCredential(new Uri(url), token);
   
               // Add the credential to the AuthenticationManager.
               AuthenticationManager.Current.AddCredential(tempToken);
           }
   
           // The ChallengeHandler function that is called when access to a secured resource is attempted.
           public static async Task<Credential> PromptCredentialAsync(CredentialRequestInfo info)
           {
               Credential credential = null;
   
               try
               {
                   // Get credentials for the specified server. The OAuthAuthorize class (defined below)
                   // will get the user's credentials (show the login window and handle the response).
                   credential = await AuthenticationManager.Current.GenerateCredentialAsync(info.ServiceUri);
               }
               catch (OperationCanceledException)
               {
                   // Login was cancelled, no need to display an error to the user.
               }
   
               return credential;
           }
   
           #region OAuth handler
   
           // In a .NET MAUI app, an IOAuthAuthorizeHandler component is used to handle some of
           // the OAuth details. Specifically, it implements AuthorizeAsync to show the login UI
           // (generated by the server that hosts secure content) in a WebAuthenticator. When the user
           // logs in successfully, cancels the login, or closes the window without continuing, the
           // IOAuthAuthorizeHandler is responsible for obtaining the authorization from the server
           // or raising an OperationCanceledException.
           public class OAuthAuthorize : IOAuthAuthorizeHandler
           {
               // Function to initiate an authorization request. It takes the URIs for: the secured service,
               // the authorization endpoint, and the redirect URI.
   #if MACCATALYST || IOS
               public Task<IDictionary<string, string>> AuthorizeAsync(Uri serviceUri, Uri authorizeUri, Uri callbackUri)
               {
                   // Use a TaskCompletionSource to track the completion of the authorization.
                   var tcs = new TaskCompletionSource<IDictionary<string, string>>();
                   Microsoft.Maui.ApplicationModel.MainThread.BeginInvokeOnMainThread(async () =>
                   {
                       try
                       {
                           var result = await WebAuthenticator.AuthenticateAsync(authorizeUri, callbackUri);
                           tcs.TrySetResult(result.Properties);
                       }
                       catch (Exception ex)
                       {
                           tcs.TrySetException(ex);
                       }
                   });
                   return tcs.Task;
               }
   #elif ANDROID
               public async Task<IDictionary<string, string>> AuthorizeAsync(Uri serviceUri, Uri authorizeUri, Uri callbackUri)
               {
                   var result = await WebAuthenticator.AuthenticateAsync(authorizeUri, callbackUri);
                   return result.Properties;
               }
   #elif WINDOWS
               // WebAuthenticator does not currently work on Windows without the WinUIEx library.
               // https://learn.microsoft.com/en-us/dotnet/maui/platform-integration/communication/authentication?tabs=windows
               public async Task<IDictionary<string, string>> AuthorizeAsync(Uri serviceUri, Uri authorizeUri, Uri callbackUri)
               {
                   var result = await WinUIEx.WebAuthenticator.AuthenticateAsync(authorizeUri, callbackUri);
   
                   return result.Properties;
               }
   
   #endif
   
   #if ANDROID
               // Android requires an Intent Filter setup to handle your callback URI.
               // This is accomplished by inheriting from the WebAuthenticatorCallbackActivity class.
               // https://learn.microsoft.com/en-us/dotnet/maui/platform-integration/communication/authentication?tabs=android
   
               [Activity(NoHistory = true, Exported = true, LaunchMode = LaunchMode.SingleTop)]
               [IntentFilter(new[] { Intent.ActionView },
                  Categories = new[] { Intent.CategoryDefault, Intent.CategoryBrowsable },
                  DataScheme = "my-app", DataHost = "auth")]
               public class WebAuthenticationCallbackActivity : WebAuthenticatorCallbackActivity
               {
               }
   
   #endif
   
               #endregion OAuth handler
   
           }
       }
   }

4. Near the top of the file, add your values for client ID (OAuthClientID) and redirect URL (OAuthRedirectUrl ). These were created with your OAuth application metadata in an earlier step and are unique to your application.

   AuthenticationHelper.cs

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       // A helper class that manages authenticating with a server to access secure resources.
       internal static class AuthenticationHelper
       {
           // Specify the client ID and redirect URL to use for OAuth authentication.
           // Create your OAuth application metadata using the ArcGIS developer dashboard:
           // https://developers.arcgis.com/dashboard/
   
           private const string OAuthClientID = "YOUR_CLIENT_ID";
           private const string OAuthRedirectUrl = "YOUR_REDIRECT_URL";
   

The AuthenticationHelper class is now set up to handle OAuth authentication in your app. This class is generic enough that you can use it in any app, as long as valid client ID and redirect URL values are provided.

The last step is to use AuthenticationHelper to register one or more server URLs with AuthenticationManager to authenticate the user for secure resources from those servers.

Register ArcGIS Online for OAuth authentication

Registering a server with AuthenticationManager ensures that the user will be authenticated for any secured resources hosted on that server. The server is registered using its URL and the type of authentication it requires (one of the token authentication types supported for ArcGIS). For OAuth authentication, you must also provide required OAuth metadata, such as the client ID and redirect URL.

1. In the Visual Studio > Solution Explorer, double-click MapViewModel.cs to open the file.

2. In the SetupMap() function, add a line of code that uses AuthenticationHelper to register ArcGIS Online for authentication.

   MapViewModel.cs

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           private void SetupMap()
           {
   
               // Add the ArcGIS Online URL to the authentication helper.
               AuthenticationHelper.RegisterSecureServer("https://www.arcgis.com/sharing/rest");
   
               // Create a new map with a 'topographic vector' basemap.
               var trafficMap = new Map(BasemapStyle.ArcGISTopographic);
   
               var mapCenterPoint = new MapPoint(-118.805, 34.027, SpatialReferences.Wgs84);
   
               trafficMap.InitialViewpoint = new Viewpoint(mapCenterPoint, 100000);
   
               // Create a layer to display the ArcGIS World Traffic service.
               var trafficServiceUrl = "https://traffic.arcgis.com/arcgis/rest/services/World/Traffic/MapServer";
               var trafficLayer = new ArcGISMapImageLayer(new Uri(trafficServiceUrl));
   
               // Handle changes in the traffic layer's load status to check for errors.
               trafficLayer.LoadStatusChanged += TrafficLayer_LoadStatusChanged;
   
               // Add the traffic layer to the map's data layer collection.
               trafficMap.OperationalLayers.Add(trafficLayer);
   
               // Set the view model Map property with the new map.
               this.Map = trafficMap;
   
           }
   

   Expand

3. Click Debug > Start Debugging (or press <F5> on the keyboard) to run the app.

You should again see a map with the topographic basemap layer centered on the Santa Monica Mountains in California. You will be prompted for an ArcGIS Online username and password. Once you authenticate successfully with ArcGIS Online, the traffic layer will appear in the map.

Testing apps that require authentication

When you are testing apps that require authentication for one or more services in the map, it can become monotonous to enter your OAuth credentials repeatedly. You can programmatically add authentication for a server using the temporary token provided with your OAuth application metadata. As the name suggests, this token is valid for a limited time, but you can always get a fresh token from the developer dashboard.

The AuthenticationHelper has the following function for applying a temporary token.

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        // A function that adds a credential to AuthenticationManager based on a temporary token.
        // This is useful for testing an app with secured services without having to log in.
        public static void ApplyTemporaryToken(string url, string token)
        {
            // Create a new OAuth credential for the specified URL with the token.
            OAuthTokenCredential tempToken = new OAuthTokenCredential(new Uri(url), token);

            // Add the credential to the AuthenticationManager.
            AuthenticationManager.Current.AddCredential(tempToken);
        }

You can call the function with code such as:

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   AuthenticationHelper.ApplyTemporaryToken("https://www.arcgis.com/sharing/rest", "YOUR_TEMP_TOKEN");

Until the token expires, you can run the app without being challenged to provide your credentials.

Additional resources

If you are implementing OAuth for another .NET platform, you might find some of the following resources helpful.

• ArcGIS Maps SDK for .NET OAuth sample: The WPF version of this sample uses code similar to code used in this tutorial. The sample is available for other .NET platforms (use the switcher control at the top of the page) to illustrate implementing OAuth for apps targeting WinUI, UWP, and .NET MAUI.
• Web authentication broker: Use this authentication broker to implement OAuth in your Universal Windows Platform (UWP) apps.