Add sample for auxiliary header

sdk/resourcemanager/Azure.ResourceManager/samples/README.md

@@ -15,3 +15,4 @@ description: Samples for the Azure.ResourceManager client library
 - [Hello World - Getting a subscription async](https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/resourcemanager/Azure.ResourceManager/samples/Sample1_HelloWorldAsync.md)
 - [Managing Resource Groups](https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/resourcemanager/Azure.ResourceManager/samples/Sample2_ManagingResourceGroups.md)
 - [Creating a virtual network](https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/resourcemanager/Azure.ResourceManager/samples/Sample3_CreatingAVirtualNetwork.md)
+- [Enable Cross-Tenant Authentication](https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/resourcemanager/Azure.ResourceManager/samples/Sample4_MultiTenant.md)

sdk/resourcemanager/Azure.ResourceManager/samples/Sample4_MultiTenant.md

@@ -0,0 +1,62 @@
+Example: Authenticate across tenants
+--------------------------------------
+For this example, you need the following namespaces:
+```C# Snippet:MultiTenant_Namespaces
+using System;
+using System.Threading.Tasks;
+using Azure.Core;
+using Azure.Identity;
+```
+
+In order to test for multi-tenant, you will need to setup a service principal for another tenant.
+1. Enable multi tenant on your SPN.
+2. Add the redirect URL under the web (not single page application), e.g. https://www.microsoft.com
+3. Using following link to add SPN to tenant2:
+    https://login.microsoftonline.com/<Tenant2_ID>/oauth2/authorize?client_id=<Client_ID>&response_type=code&redirect_uri=https%3A%2F%2Fwww.microsoft.com%2F
+4. Give enough permission for the SPN in both tenants/subscriptions.
+5. Set related environment variables to your machine.
+
+***Create a pipeline policy***
+
+```C# Snippet:Sample_Header_Policy
+public class AuxiliaryPoilcy : HttpPipelineSynchronousPolicy
+{
+    private static string AUTHORIZATION_AUXILIARY_HEADER = "x-ms-authorization-auxiliary";
+    string _token;
+
+    public AuxiliaryPoilcy(string token)
+    {
+        _token = token;
+    }
+
+    public override void OnSendingRequest(HttpMessage message)
+    {
+        string token = "Bearer " + _token;
+        if (!message.Request.Headers.TryGetValue(AUTHORIZATION_AUXILIARY_HEADER, out _))
+        {
+            message.Request.Headers.Add(AUTHORIZATION_AUXILIARY_HEADER, token);
+        }
+    }
+}
+```
+
+***Authenticate the client and add token to the header***
+
+```C# Snippet:Enable_Cross_Tenant_Authentication
+string clientId = Environment.GetEnvironmentVariable("CLIENT_ID");
+string clientSecret = Environment.GetEnvironmentVariable("CLIENT_SECRET");
+string tenantId01 = Environment.GetEnvironmentVariable("TENANT_ID_01");
+string tenantId02 = Environment.GetEnvironmentVariable("TENANT_ID_02");
+string subscriptionId01 = Environment.GetEnvironmentVariable("SUBSCRIPTION_ID_01");
+
+// Prepare client and policy for tenant01
+ClientSecretCredential credForTenant01 = new ClientSecretCredential(tenantId01, clientId, clientSecret);
+ClientSecretCredential credForTenant02 = new ClientSecretCredential(tenantId02, clientId, clientSecret);
+
+string token = (await credForTenant02.GetTokenAsync(new Azure.Core.TokenRequestContext(
+        new[] { "https://management.azure.com/.default" }))).Token;
+ArmClientOptions options = new ArmClientOptions();
+AuxiliaryPoilcy headerPolicy = new AuxiliaryPoilcy(token);
+options.AddPolicy(headerPolicy, HttpPipelinePosition.PerCall);
+ArmClient client = new ArmClient(credForTenant01, subscriptionId01, options);
+```

sdk/resourcemanager/Azure.ResourceManager/tests/Samples/AuxiliaryPoilcy.cs

@@ -0,0 +1,27 @@
+using Azure.Core;
+using Azure.Core.Pipeline;
+
+namespace Azure.ResourceManager.Tests.Samples
+{
+    #region Snippet:Sample_Header_Policy
+    public class AuxiliaryPoilcy : HttpPipelineSynchronousPolicy
+    {
+        private static string AUTHORIZATION_AUXILIARY_HEADER = "x-ms-authorization-auxiliary";
+        string _token;
+
+        public AuxiliaryPoilcy(string token)
+        {
+            _token = token;
+        }
+
+        public override void OnSendingRequest(HttpMessage message)
+        {
+            string token = "Bearer " + _token;
+            if (!message.Request.Headers.TryGetValue(AUTHORIZATION_AUXILIARY_HEADER, out _))
+            {
+                message.Request.Headers.Add(AUTHORIZATION_AUXILIARY_HEADER, token);
+            }
+        }
+    }
+    #endregion
+}

sdk/resourcemanager/Azure.ResourceManager/tests/Samples/Sample4_MultiTenant.cs

@@ -0,0 +1,37 @@
+#region Snippet:MultiTenant_Namespaces
+using System;
+using System.Threading.Tasks;
+using Azure.Core;
+using Azure.Identity;
+#endregion
+using NUnit.Framework;
+
+namespace Azure.ResourceManager.Tests.Samples
+{
+    public class Sample4_MultiTenant
+    {
+        [Test]
+        [Ignore("Only verifying that the sample builds")]
+        public async Task EnableCrossTenantAuthentication()
+        {
+            #region Snippet:Enable_Cross_Tenant_Authentication
+            string clientId = Environment.GetEnvironmentVariable("CLIENT_ID");
+            string clientSecret = Environment.GetEnvironmentVariable("CLIENT_SECRET");
+            string tenantId01 = Environment.GetEnvironmentVariable("TENANT_ID_01");
+            string tenantId02 = Environment.GetEnvironmentVariable("TENANT_ID_02");
+            string subscriptionId01 = Environment.GetEnvironmentVariable("SUBSCRIPTION_ID_01");
+
+            // Prepare client and policy for tenant01
+            ClientSecretCredential credForTenant01 = new ClientSecretCredential(tenantId01, clientId, clientSecret);
+            ClientSecretCredential credForTenant02 = new ClientSecretCredential(tenantId02, clientId, clientSecret);
+
+            string token = (await credForTenant02.GetTokenAsync(new Azure.Core.TokenRequestContext(
+                    new[] { "https://management.azure.com/.default" }))).Token;
+            ArmClientOptions options = new ArmClientOptions();
+            AuxiliaryPoilcy headerPolicy = new AuxiliaryPoilcy(token);
+            options.AddPolicy(headerPolicy, HttpPipelinePosition.PerCall);
+            ArmClient client = new ArmClient(credForTenant01, subscriptionId01, options);
+            #endregion
+        }
+    }
+}