added dotnet sample using Azure AD authentication

quickstart/dotnet-aad/KafkaProducer/KafkaProducer.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net5.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Azure.Identity" Version="1.4.0" />
+    <PackageReference Include="Confluent.Kafka" Version="1.7.0" />
+  </ItemGroup>
+
+</Project>

quickstart/dotnet-aad/KafkaProducer/Program.cs

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+using Azure.Core;
+using Azure.Identity;
+using Confluent.Kafka;
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace KafkaProducer
+{
+    class Program
+    {
+
+        private static string eventHubNamespaceFQDNwithPort = "<event hub namespace name>.servicebus.windows.net:9093";
+
+        private static string eventHubNamespace = "<event hub namespace name>";
+
+        // connectionstring - primary or secondary key
+        private static string policyConnectionString = "Endpoint=sb://<event hub namespace name>.servicebus.windows.net/;SharedAccessKeyName=<policy name>;SharedAccessKey=<policy key>;EntityPath=<event hub name>";
+
+        //in kafka world this is the topic in event hub is the event hub name under the namespace
+        private static string topicName = "<event hub name>";
+
+
+
+
+
+        static async Task Main(string[] args)
+        {
+			Console.WriteLine("Hello Event Hub Kafka client!");
+
+			//remember to proberly feed the following static attributes:
+			//eventHubNamespace 
+			//eventHubNamespaceFQDNwithPort
+
+
+			try
+			{
+				//----- SAS AUTH -----//
+				//
+				//to leverage SAS Key as authentication methods we need the following static attribute valorized in the code:
+				//policyConnectionString
+				//
+				//var producer = GetProducerSAS();
+				//
+				//----- -------- -----//
+
+
+				//----- AAD AUTH -----//
+				//
+				//to leverage AAD as authentication methods you need to provide to the application a valid principal informations according to what's needed by DefaultAzureCredentialOptions
+				//
+				//Get a Producer using an AAD Token
+				var producer = GetProducerAADToken();
+				//
+				//----- -------- -----//
+
+				Console.WriteLine("Initiating Execution");
+
+				for (int x = 0; x < 100; x++)
+				{
+					var msg = new Message<Null, string> { Value = string.Format("This is a sample message - msg # {0} at {1}", x, DateTime.Now.ToString("yyyMMdd_HHmmSSfff")) };
+
+					// publishes the message to Event Hubs
+					var result = await producer.ProduceAsync(topicName, msg);
+
+					Console.WriteLine($"Message {result.Value} sent to partition {result.TopicPartition } with result {result.Status}");
+				}
+
+			}
+			catch (Exception e)
+			{
+				Console.WriteLine(string.Format("Exception Ocurred - {0}", e.Message));
+			}
+		}
+
+
+		/// <summary>
+		/// Kafka Client callback to get or refresh a Token
+		/// </summary>
+		/// <param name="client"></param>
+		/// <param name="cfg"></param>
+		static void OAuthTokenRefreshCallback(IClient client, string cfg)
+		{
+            try
+            {
+                DefaultAzureCredentialOptions defaultAzureCredentialOptions = new DefaultAzureCredentialOptions();
+                DefaultAzureCredential defaultAzureCredential = new DefaultAzureCredential(defaultAzureCredentialOptions);
+
+                var tokenRequestContext = new TokenRequestContext(new string[] { $"https://{eventHubNamespace}.servicebus.windows.net/.default" });
+
+                var accessToken = defaultAzureCredential.GetToken(tokenRequestContext);
+
+
+                var token = accessToken.Token;
+                var expire = accessToken.ExpiresOn.ToUnixTimeMilliseconds();
+
+                //principal could be null for Kafka OAuth 2.0 auth
+                client.OAuthBearerSetToken(token, expire, null);
+            }
+            catch (Exception ex)
+            {
+				client.OAuthBearerSetTokenFailure(ex.ToString());
+			}
+		}
+
+
+
+		private static IProducer<Null, string> GetProducerAADToken()
+		{
+			var pConfig = new ProducerConfig
+			{
+				BootstrapServers = eventHubNamespaceFQDNwithPort,
+				SaslMechanism = SaslMechanism.OAuthBearer,
+				SecurityProtocol = SecurityProtocol.SaslSsl,
+				BrokerVersionFallback = "0.10.0.0",
+				ApiVersionFallbackMs = 0,
+				Debug = "security,broker,protocol"
+			};
+
+			//instantiates the producer
+			var producerBuilder = new ProducerBuilder<Null, string>(pConfig);
+
+			//configure the call back to grab a token
+			IProducer<Null, string> producer = producerBuilder.SetOAuthBearerTokenRefreshHandler(OAuthTokenRefreshCallback).Build();
+
+			return producer;
+		}
+
+
+		private static IProducer<Null, string> GetProducerSAS()
+		{
+			//for Plain Sasl mechanism use an hard coded naming convention for user name and use the connection string as password
+
+			var pConfig = new ProducerConfig
+			{
+				BootstrapServers = eventHubNamespaceFQDNwithPort,
+				SaslMechanism = SaslMechanism.Plain,
+				SecurityProtocol = SecurityProtocol.SaslSsl,
+				SaslUsername = "$ConnectionString",
+				SaslPassword = policyConnectionString,
+				BrokerVersionFallback = "0.10.0.0",
+				ApiVersionFallbackMs = 0,
+				Debug = "security,broker,protocol"
+			};
+
+			//instantiates the producer
+			var producerBuilder = new ProducerBuilder<Null, string>(pConfig);
+
+			IProducer<Null, string> producer = producerBuilder.Build();
+
+			return producer;
+		}
+
+	}
+}

quickstart/dotnet-aad/KafkaSampleApps.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 16
+VisualStudioVersion = 16.0.31424.327
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "KafkaProducer", "KafkaProducer\KafkaProducer.csproj", "{4567B897-BC03-4D9B-BB1D-83469CC97FF6}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{4567B897-BC03-4D9B-BB1D-83469CC97FF6}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{4567B897-BC03-4D9B-BB1D-83469CC97FF6}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{4567B897-BC03-4D9B-BB1D-83469CC97FF6}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{4567B897-BC03-4D9B-BB1D-83469CC97FF6}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {2813E88D-9F06-47AC-B2C2-2A176437B8CA}
+	EndGlobalSection
+EndGlobal

quickstart/dotnet-aad/README.md

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+# Event Hub Kafka endpoint Azure AD Authentication using C#
+
+Event Hub is a big-data streaming platform and event ingestion service part of the messaging service ecosystem in Azure
+
+Event Hub for Kafka support both SAS (shared access signatures) and OAuth 2.0 (in our case Azure AD).
+
+I started to look for sample code around using a C# library authenticating with an OAuth 2.0 token obtained from Azure AD but I didn't found anything, so I decided to create my sample code and the best .NET Kafka library I found out there it was the “Confluent.Kafka”.
+
+This sample will connect to Event Hub kafka endpoint using the Confluent.Kafka library grabbing an Azure AD Access Token with the help of the Azure.Identity library. 
+
+
+## Executing the sample 
+
+In order to execute the sample code you need to fill some variable with some configuration of your Event Hub (of course for production grade app this stuff should come from a configuration and not hardcoded into the code).
+
+    private static string eventHubNamespaceFQDNwithPort = "<event hub namespace name>.servicebus.windows.net:9093";
+
+    private static string eventHubNamespace = "<event hub namespace name>";
+
+    // connectionstring - primary or secondary key
+    private static string policyConnectionString = "Endpoint=sb://<event hub namespace name>.servicebus.windows.net/;SharedAccessKeyName=<policy name>;SharedAccessKey=<policy key>;EntityPath=<event hub name>";
+
+    //in kafka world this is the topic in event hub is the event hub name under the namespace
+    private static string topicName = "<event hub name>";
+
+
+The, the code leverage the Azure.Identity package, in particular the 'DefaultAzureCredentialOptions' class to obtain a token.
+Please follo the instruction on the article you find linked at the bottom to configure a Principal and provide the secret to this sample app. 
+
+
+    static void OAuthTokenRefreshCallback(IClient client, string cfg)
+    {
+        try
+        {
+            DefaultAzureCredentialOptions defaultAzureCredentialOptions = new DefaultAzureCredentialOptions();
+            DefaultAzureCredential defaultAzureCredential = new DefaultAzureCredential(defaultAzureCredentialOptions);
+
+            var tokenRequestContext = new TokenRequestContext(new string[] { $"https://{eventHubNamespace}.servicebus.windows.net/.default" });
+
+            var accessToken = defaultAzureCredential.GetToken(tokenRequestContext);
+
+
+            var token = accessToken.Token;
+            var expire = accessToken.ExpiresOn.ToUnixTimeMilliseconds();
+
+            //principal could be null for Kafka OAuth 2.0 auth
+            client.OAuthBearerSetToken(token, expire, null);
+        }
+        catch (Exception ex)
+        {
+            client.OAuthBearerSetTokenFailure(ex.ToString());
+        }
+    }
+
+
+
+
+## Microsoft Techcommunity Blog Post
+
+You can find the full blog post at this url:
+https://techcommunity.microsoft.com/t5/fasttrack-for-azure/event-hub-kafka-endpoint-azure-ad-authentication-using-c/ba-p/2586185
+
+
+