chore: import upstream snapshot with attribution

dotnet/samples/02-agents/AgentProviders/foundry/Agent_Step08_DependencyInjection/Agent_Step08_DependencyInjection.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFrameworks>net10.0</TargetFrameworks>
+
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+
+    <NoWarn>$(NoWarn);CA1812</NoWarn>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.Hosting" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\..\..\src\Microsoft.Agents.AI.Foundry\Microsoft.Agents.AI.Foundry.csproj" />
+  </ItemGroup>
+
+</Project>

dotnet/samples/02-agents/AgentProviders/foundry/Agent_Step08_DependencyInjection/Program.cs

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+// Copyright (c) Microsoft. All rights reserved.
+
+// This sample shows how to use dependency injection to register a AIAgent and use it from a hosted service.
+
+using Azure.AI.Projects;
+using Azure.Identity;
+using Microsoft.Agents.AI;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using SampleApp;
+
+string endpoint = Environment.GetEnvironmentVariable("FOUNDRY_PROJECT_ENDPOINT") ?? throw new InvalidOperationException("FOUNDRY_PROJECT_ENDPOINT is not set.");
+string deploymentName = Environment.GetEnvironmentVariable("FOUNDRY_MODEL") ?? "gpt-5.4-mini";
+
+// 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.
+AIProjectClient aiProjectClient = new(new Uri(endpoint), new DefaultAzureCredential());
+
+AIAgent agent = aiProjectClient.AsAIAgent(deploymentName,
+    instructions: "You are good at telling jokes.",
+    name: "JokerAgent");
+
+// Create a host builder that we will register services with and then run.
+HostApplicationBuilder builder = Host.CreateApplicationBuilder(args);
+
+// Add the AI agent to the service collection.
+builder.Services.AddSingleton(agent);
+
+// 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);
+
+namespace SampleApp
+{
+    /// <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)
+        {
+            this._session = await agent.CreateSessionAsync(cancellationToken);
+            _ = this.RunAsync(appLifetime.ApplicationStopping);
+        }
+
+        public async Task RunAsync(CancellationToken cancellationToken)
+        {
+            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("> ");
+                string? input = Console.ReadLine();
+
+                if (string.IsNullOrWhiteSpace(input))
+                {
+                    appLifetime.StopApplication();
+                    break;
+                }
+
+                await foreach (AgentResponseUpdate update in agent.RunStreamingAsync(input, this._session, cancellationToken: cancellationToken))
+                {
+                    Console.Write(update);
+                }
+
+                Console.WriteLine();
+            }
+        }
+
+        public Task StopAsync(CancellationToken cancellationToken)
+        {
+            Console.WriteLine("\nShutting down...");
+            return Task.CompletedTask;
+        }
+    }
+}

dotnet/samples/02-agents/AgentProviders/foundry/Agent_Step08_DependencyInjection/README.md

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+# Dependency Injection with the Responses API
+
+This sample demonstrates how to register a `ChatClientAgent` in a dependency injection container and use it from a hosted service.
+
+## What this sample demonstrates
+
+- Registering `ChatClientAgent` as an `AIAgent` in the service collection
+- Using the agent from a `IHostedService` with an interactive chat loop
+- Streaming responses in a hosted service context
+- No server-side agent creation or cleanup required
+
+## Prerequisites
+
+- .NET 10 SDK or later
+- Microsoft Foundry service endpoint and deployment configured
+- An authenticated Azure identity (for example, sign in with `az login`)
+
+Set the following environment variables:
+
+```powershell
+$env:FOUNDRY_PROJECT_ENDPOINT="https://your-foundry-service.services.ai.azure.com/api/projects/your-foundry-project"
+$env:FOUNDRY_MODEL="gpt-5.4-mini"
+```
+
+## Run the sample
+
+```powershell
+cd dotnet/samples/02-agents/AgentProviders/foundry
+dotnet run --project .\Agent_Step08_DependencyInjection
+```
+