.NET - Reorder Agents samples to start from Step01 instead of Step04 (#4110)

dotnet/samples/02-agents/Agents/Agent_Step06_DependencyInjection/Program.cs

@@ -0,0 +1,88 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+#pragma warning disable CA1812
+
+// This sample shows how to use dependency injection to register an AIAgent and use it from a hosted service with a user input chat loop.
+
+using Azure.AI.OpenAI;
+using Azure.Identity;
+using Microsoft.Agents.AI;
+using Microsoft.Extensions.AI;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+
+var endpoint = Environment.GetEnvironmentVariable("AZURE_OPENAI_ENDPOINT") ?? throw new InvalidOperationException("AZURE_OPENAI_ENDPOINT is not set.");
+var deploymentName = Environment.GetEnvironmentVariable("AZURE_OPENAI_DEPLOYMENT_NAME") ?? "gpt-4o-mini";
+
+// Create a host builder that we will register services with and then run.
+HostApplicationBuilder builder = Host.CreateApplicationBuilder(args);
+
+// Add agent options to the service collection.
+builder.Services.AddSingleton(new ChatClientAgentOptions() { Name = "Joker", ChatOptions = new() { Instructions = "You are good at telling jokes." } });
+
+// Add a chat client to the service collection.
+// WARNING: DefaultAzureCredential is convenient for development but requires careful consideration in production.
+// In production, consider using a specific credential (e.g., ManagedIdentityCredential) to avoid
+// latency issues, unintended credential probing, and potential security risks from fallback mechanisms.
+builder.Services.AddKeyedChatClient("AzureOpenAI", (sp) => new AzureOpenAIClient(
+    new Uri(endpoint),
+    new DefaultAzureCredential())
+        .GetChatClient(deploymentName)
+        .AsIChatClient());
+
+// Add the AI agent to the service collection.
+builder.Services.AddSingleton<AIAgent>((sp) => new ChatClientAgent(
+    chatClient: sp.GetRequiredKeyedService<IChatClient>("AzureOpenAI"),
+    options: sp.GetRequiredService<ChatClientAgentOptions>()));
+
+// Add a sample service that will use the agent to respond to user input.
+builder.Services.AddHostedService<SampleService>();
+
+// Build and run the host.
+using IHost host = builder.Build();
+await host.RunAsync().ConfigureAwait(false);
+
+/// <summary>
+/// A sample service that uses an AI agent to respond to user input.
+/// </summary>
+internal sealed class SampleService(AIAgent agent, IHostApplicationLifetime appLifetime) : IHostedService
+{
+    private AgentSession? _session;
+
+    public async Task StartAsync(CancellationToken cancellationToken)
+    {
+        // Create a session that will be used for the entirety of the service lifetime so that the user can ask follow up questions.
+        this._session = await agent.CreateSessionAsync(cancellationToken);
+        _ = this.RunAsync(appLifetime.ApplicationStopping);
+    }
+
+    public async Task RunAsync(CancellationToken cancellationToken)
+    {
+        // Delay a little to allow the service to finish starting.
+        await Task.Delay(100, cancellationToken);
+
+        while (!cancellationToken.IsCancellationRequested)
+        {
+            Console.WriteLine("\nAgent: Ask me to tell you a joke about a specific topic. To exit just press Ctrl+C or enter without any input.\n");
+            Console.Write("> ");
+            var input = Console.ReadLine();
+
+            // If the user enters no input, signal the application to shut down.
+            if (string.IsNullOrWhiteSpace(input))
+            {
+                appLifetime.StopApplication();
+                break;
+            }
+
+            // Stream the output to the console as it is generated.
+            await foreach (var update in agent.RunStreamingAsync(input, this._session, cancellationToken: cancellationToken))
+            {
+                Console.Write(update);
+            }
+
+            Console.WriteLine();
+        }
+    }
+
+    public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
+}