Add AAD sample to README. (Azure#22722)

* Add AAD sample to README.

* Increase sleep time to allow permissions to propagate

Author: JoshLove-msft

sdk/eventgrid/Azure.Messaging.EventGrid/README.md

@@ -38,15 +38,18 @@ The access key can also be found through the [portal](https://docs.microsoft.com
 az eventgrid topic key list --name <your-resource-name> --resource-group <your-resource-group-name> --query "key1"
 ```
 
-#### Creating and Authenticating `EventGridPublisherClient`
+#### Authenticate using Topic Access Key
 
 Once you have your access key and topic endpoint, you can create the publisher client as follows:
 ```C#
 EventGridPublisherClient client = new EventGridPublisherClient(
     new Uri("<endpoint>"),
     new AzureKeyCredential("<access-key>"));
 ```
-Event Grid also supports authenticating with a shared access signature which allows for providing access to a resource that expires by a certain time without sharing your access key. 
+
+#### Authenticate using Shared Access Signature
+
+Event Grid also supports authenticating with a shared access signature which allows for providing access to a resource that expires by a certain time without sharing your access key.
 Generally, the workflow would be that one application would generate the SAS string and hand off the string to another application that would consume the string.
 Generate the SAS:
 ```C# Snippet:GenerateSas
@@ -65,6 +68,18 @@ EventGridPublisherClient client = new EventGridPublisherClient(
 
 `EventGridPublisherClient` also accepts a set of configuring options through `EventGridPublisherClientOptions`. For example, you can specify a custom serializer that will be used to serialize the event data to JSON.
 
+#### Authenticate using Azure Active Directory
+
+Azure Event Grid provides integration with Azure Active Directory (Azure AD) for identity-based authentication of requests. With Azure AD, you can use role-based access control (RBAC) to grant access to your Azure Event Grid resources to users, groups, or applications. The [Azure Identity library](https://github.com/Azure/azure-sdk-for-net/tree/main/sdk/identity/Azure.Identity/README.md) provides easy Azure Active Directory support for authentication.
+
+To send events to a topic or domain using Azure Active Directory, the authenticated identity should have the "EventGrid Data Sender" role assigned.
+
+```C# Snippet:EventGridAAD
+EventGridPublisherClient client = new EventGridPublisherClient(
+    new Uri(topicEndpoint),
+    new DefaultAzureCredential());
+```
+
 ## Key concepts
 
 For information about general Event Grid concepts: [Concepts in Azure Event Grid](https://docs.microsoft.com/azure/event-grid/concepts).
@@ -264,7 +279,7 @@ foreach (CloudEvent cloudEvent in cloudEvents)
 
 Using `TryGetSystemEventData()`:
 
-If expecting mostly system events, it may be cleaner to switch on `TryGetSystemEventData()` and use pattern matching to act on the individual events. If an event is not a system event, the method will return false and the out parameter will be null. 
+If expecting mostly system events, it may be cleaner to switch on `TryGetSystemEventData()` and use pattern matching to act on the individual events. If an event is not a system event, the method will return false and the out parameter will be null.
 
 *As a caveat, if you are using a custom event type with an EventType value that later gets added as a system event by the service and SDK, the return value of `TryGetSystemEventData` would change from `false` to `true`. This could come up if you are pre-emptively creating your own custom events for events that are already being sent by the service, but have not yet been added to the SDK. In this case, it is better to use the generic `GetData<T>` method so that your code flow doesn't change automatically after upgrading (of course, you may still want to modify your code to consume the newly released system event model as opposed to your custom model).*
 
@@ -323,7 +338,7 @@ You can also easily [enable console logging](https://github.com/Azure/azure-sdk-
 ### Distributed Tracing
 The Event Grid library supports distributing tracing out of the box. In order to adhere to the CloudEvents specification's [guidance](https://github.com/cloudevents/spec/blob/master/extensions/distributed-tracing.md) on distributing tracing, the library will set the `traceparent` and `tracestate` on the `ExtensionAttributes` of a `CloudEvent` when distributed tracing is enabled. To learn more about how to enable distributed tracing in your application, take a look at the Azure SDK [distributed tracing documentation](https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/core/Azure.Core/samples/Diagnostics.md#Distributed-tracing).
 
-### Event Grid on Kubernetes 
+### Event Grid on Kubernetes
 This library has been tested and validated on Kubernetes using Azure Arc.
 
 ## Next steps

sdk/eventgrid/Azure.Messaging.EventGrid/tests/Samples/Sample1_SendEventsToTopicAndDomain.cs

@@ -108,6 +108,31 @@ public async Task AuthenticateWithSasToken()
             await client.SendEventsAsync(eventsList);
         }
 
+        [Test]
+        public async Task AuthenticateWithAAD()
+        {
+            string topicEndpoint = TestEnvironment.TopicHost;
+
+            #region Snippet:EventGridAAD
+            EventGridPublisherClient client = new EventGridPublisherClient(
+                new Uri(topicEndpoint),
+                new DefaultAzureCredential());
+            #endregion
+
+            // Add EventGridEvents to a list to publish to the topic
+            List<EventGridEvent> eventsList = new List<EventGridEvent>
+            {
+                new EventGridEvent(
+                    "ExampleEventSubject",
+                    "Example.EventType",
+                    "1.0",
+                    "This is the event data")
+            };
+
+            // Send the events
+            await client.SendEventsAsync(eventsList);
+        }
+
         // This sample demonstrates how to publish CloudEvents 1.0 schema events to an Event Grid topic.
         [Test]
         public async Task SendCloudEventsToTopic()

sdk/eventgrid/test-resources-post.ps1

@@ -12,5 +12,5 @@ param (
     [string] $TestApplicationSecret
 )
 
-Write-Verbose "Sleeping for 60 seconds to let RBAC replicate"
-Start-Sleep -s 60
+Write-Verbose "Sleeping for 120 seconds to let RBAC replicate"
+Start-Sleep -s 120