update the way to setup access token for dotnet face client

Author: der3318

articles/ai-services/computer-vision/how-to/identity-access-token.md

@@ -112,61 +112,51 @@ curl -X POST 'https://<client-endpoint>/face/v1.0/identify' \
 
 #### [C#](#tab/csharp)
 
-The following code snippets show you how to use an access token with the [Face SDK for C#](https://www.nuget.org/packages/Microsoft.Azure.CognitiveServices.Vision.Face).
+The following code snippets show you how to use an access token with the [Face SDK for C#](https://aka.ms/azsdk-csharp-face-pkg).
 
-The following class uses an access token to create a **ServiceClientCredentials** object that can be used to authenticate a Face API client object. It automatically adds the access token as a header in every request that the Face client will make.
+The following class uses an access token to create a **HttpPipelineSynchronousPolicy** object that can be used to authenticate a Face API client object. It automatically adds the access token as a header in every request that the Face client will make.
 
 ```csharp
-public class LimitedAccessTokenWithApiKeyClientCredential : ServiceClientCredentials 
+public class LimitedAccessTokenPolicy : HttpPipelineSynchronousPolicy
 {
-    /// <summary> 
-    /// Creates a new instance of the LimitedAccessTokenWithApiKeyClientCredential class 
-    /// </summary> 
-    /// <param name="apiKey">API Key for the Face API or CognitiveService endpoint</param> 
-    /// <param name="limitedAccessToken">LimitedAccessToken to bypass the limited access program, requires ISV sponsership.</param> 
-
-    public LimitedAccessTokenWithApiKeyClientCredential(string apiKey, string limitedAccessToken) 
-    { 
-        this.ApiKey = apiKey; 
-        this.LimitedAccessToken = limitedAccessToken; 
+    /// <summary>
+    /// Creates a new instance of the LimitedAccessTokenPolicy class
+    /// </summary>
+    /// <param name="limitedAccessToken">LimitedAccessToken to bypass the limited access program, requires ISV sponsership.</param>
+    public LimitedAccessTokenPolicy(string limitedAccessToken)
+    {
+        this.LimitedAccessToken = limitedAccessToken;
     }
 
-    private readonly string ApiKey; 
-    private readonly string LimitedAccesToken; 
-
-    /// <summary> 
-    /// Add the Basic Authentication Header to each outgoing request 
-    /// </summary> 
-    /// <param name="request">The outgoing request</param>
-    /// <param name="cancellationToken">A token to cancel the operation</param> 
-    public override Task ProcessHttpRequestAsync(HttpRequestMessage request, CancellationToken cancellationToken) 
-    { 
-        if (request == null) 
-            throw new ArgumentNullException("request"); 
-        request.Headers.Add("Ocp-Apim-Subscription-Key", ApiKey); 
-        request.Headers.Add("LimitedAccessToken", $"Bearer {LimitedAccesToken}");
-
-        return Task.FromResult<object>(null); 
-    } 
-} 
+    private readonly string LimitedAccessToken;
+
+    /// <summary>
+    /// Add the authentication header to each outgoing request
+    /// </summary>
+    /// <param name="message">The outgoing message</param>
+    public override void OnSendingRequest(HttpMessage message)
+    {
+        message.Request.Headers.Add("LimitedAccessToken", $"Bearer {LimitedAccessToken}");
+    }
+}
 ```
 
 In the client-side application, the helper class can be used like in this example:
 
 ```csharp
-static void Main(string[] args) 
-{ 
+static void Main(string[] args)
+{
     // create Face client object
-    var faceClient = new FaceClient(new LimitedAccessTokenWithApiKeyClientCredential(apiKey: "<client-face-key>", limitedAccessToken: "<token>")); 
-
-    faceClient.Endpoint = "https://mytest-eastus2.cognitiveservices.azure.com"; 
+    var clientOptions = new AzureAIVisionFaceClientOptions();
+    clientOptions.AddPolicy(new LimitedAccessTokenPolicy("<token>"), HttpPipelinePosition.PerCall);
+    FaceClient faceClient = new FaceClient(new Uri("<client-endpoint>"), new AzureKeyCredential("<client-face-key>"), clientOptions);
 
     // use Face client in an API call
-    using (var stream = File.OpenRead("photo.jpg")) 
+    using (var stream = File.OpenRead("photo.jpg"))
     {
-        var result = faceClient.Face.DetectWithStreamAsync(stream, detectionModel: "Detection_03", recognitionModel: "Recognition_04", returnFaceId: true).Result; 
+        var response = faceClient.DetectAsync(BinaryData.FromStream(stream), FaceDetectionModel.Detection03, FaceRecognitionModel.Recognition04, returnFaceId: true).Result;
 
-        Console.WriteLine(JsonConvert.SerializeObject(result)); 
+        Console.WriteLine(JsonConvert.SerializeObject(response.Value));
     }
 }
 ```