.NET: Add Handoff sample

dotnet/agent-framework-dotnet.slnx

@@ -243,6 +243,9 @@
   <Folder Name="/Samples/03-workflows/HumanInTheLoop/">
     <Project Path="samples/03-workflows/HumanInTheLoop/HumanInTheLoopBasic/HumanInTheLoopBasic.csproj" />
   </Folder>
+  <Folder Name="/Samples/03-workflows/Orchestration/">
+    <Project Path="samples/03-workflows/Orchestration/Handoff/Handoff.csproj" />
+  </Folder>
   <Folder Name="/Samples/03-workflows/Observability/">
     <Project Path="samples/03-workflows/Observability/ApplicationInsights/ApplicationInsights.csproj" />
     <Project Path="samples/03-workflows/Observability/AspireDashboard/AspireDashboard.csproj" />
@@ -288,7 +291,7 @@
     <File Path="samples/04-hosting/A2A/README.md" />
     <Project Path="samples/04-hosting/A2A/A2AAgent_AsFunctionTools/A2AAgent_AsFunctionTools.csproj" />
     <Project Path="samples/04-hosting/A2A/A2AAgent_PollingForTaskCompletion/A2AAgent_PollingForTaskCompletion.csproj" />
-  </Folder>  
+  </Folder>
   <Folder Name="/Samples/05-end-to-end/">
     <Project Path="samples/05-end-to-end/AgentWithPurview/AgentWithPurview.csproj" />
     <Project Path="samples/05-end-to-end/M365Agent/M365Agent.csproj" />

dotnet/samples/03-workflows/Orchestration/Handoff/AgentRegistry.cs

@@ -0,0 +1,72 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Microsoft.Agents.AI;
+using Microsoft.Agents.AI.Workflows;
+using Microsoft.Extensions.AI;
+
+/// <summary>
+/// The registry of agents used in the workflow.
+/// </summary>
+/// <param name="chatClient">The <see cref="IChatClient"/> to use as the agent backend.</param>
+internal sealed class AgentRegistry(IChatClient chatClient)
+{
+    internal const string IntakeAgentName = "Assistant";
+    public AIAgent IntakeAgent { get; } = chatClient.AsAIAgent(
+        instructions:
+            """
+                You receive a user request and are responsible for routing to the correct initial expert agent.
+                """,
+        IntakeAgentName
+        );
+
+    internal const string LiquidityAnalysisAgentName = "Liquidity Analysis";
+    public AIAgent LiquidityAnalysisAgent { get; } = chatClient.AsAIAgent(
+        instructions:
+            """
+                You are responsible for Liquidity Analysis.
+                """,
+        LiquidityAnalysisAgentName
+        );
+
+    internal const string TaxAnalysisAgentName = "Tax Analysis";
+    public AIAgent TaxAnalysisAgent { get; } = chatClient.AsAIAgent(
+        instructions:
+            """
+                You are responsible for Tax Analysis. 
+                """,
+        TaxAnalysisAgentName
+        );
+
+    internal const string ForeignExchangeAgentName = "Foreign Exchange Analysis";
+    public AIAgent ForeignExchangeAgent { get; } = chatClient.AsAIAgent(
+        instructions:
+            """
+                You are responsible for Foreign Exchange Analysis. 
+                """,
+        ForeignExchangeAgentName
+        );
+
+    internal const string EquityAgentName = "Equity Analysis";
+    public AIAgent EquityAgent { get; } = chatClient.AsAIAgent(
+        instructions:
+            """
+                You are responsible for Equity Analysis. 
+                """,
+        EquityAgentName
+        );
+
+    public IEnumerable<AIAgent> Experts => [this.LiquidityAnalysisAgent, this.TaxAnalysisAgent, this.ForeignExchangeAgent, this.EquityAgent];
+
+    public HashSet<AIAgent> All
+    {
+        get
+        {
+            if (field == null)
+            {
+                field = [this.IntakeAgent, .. this.Experts];
+            }
+
+            return field;
+        }
+    }
+}

dotnet/samples/03-workflows/Orchestration/Handoff/Handoff.csproj

@@ -0,0 +1,29 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFrameworks>net10.0</TargetFrameworks>
+
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+
+    <NoWarn>MAAIW001</NoWarn>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Azure.AI.Projects" />
+    <PackageReference Include="Azure.Identity" />
+    <PackageReference Include="Microsoft.Extensions.AI.OpenAI" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\..\src\Microsoft.Agents.AI.Workflows\Microsoft.Agents.AI.Workflows.csproj" />
+    <ProjectReference Include="..\..\..\..\src\Microsoft.Agents.AI\Microsoft.Agents.AI.csproj" />
+    <!-- Include Workflows source generator when using [MessageHandler] attribute -->
+    <ProjectReference Include="$(RepoRoot)/dotnet/src/Microsoft.Agents.AI.Workflows.Generators/Microsoft.Agents.AI.Workflows.Generators.csproj"
+                      OutputItemType="Analyzer"
+                      ReferenceOutputAssembly="false"
+                      GlobalPropertiesToRemove="TargetFramework" />
+  </ItemGroup>
+
+</Project>

dotnet/samples/03-workflows/Orchestration/Handoff/Handoff.sln

@@ -0,0 +1,24 @@
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.5.2.0
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Handoff", "Handoff.csproj", "{2BF9227D-128C-52CD-C43E-E51BD268AB65}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{2BF9227D-128C-52CD-C43E-E51BD268AB65}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{2BF9227D-128C-52CD-C43E-E51BD268AB65}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{2BF9227D-128C-52CD-C43E-E51BD268AB65}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{2BF9227D-128C-52CD-C43E-E51BD268AB65}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {CF541D9A-AD24-4553-A5A6-2F9FFEDD6C56}
+	EndGlobalSection
+EndGlobal

dotnet/samples/03-workflows/Orchestration/Handoff/Program.cs

@@ -0,0 +1,125 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Azure.AI.Projects;
+using Azure.Identity;
+using Microsoft.Agents.AI;
+using Microsoft.Agents.AI.Workflows;
+using Microsoft.Extensions.AI;
+
+string endpoint = Environment.GetEnvironmentVariable("AZURE_AI_PROJECT_ENDPOINT")
+            ?? throw new InvalidOperationException("AZURE_AI_PROJECT_ENDPOINT is not set.");
+string deploymentName = Environment.GetEnvironmentVariable("AZURE_AI_MODEL_DEPLOYMENT_NAME") ?? "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 projectClient = new(new Uri(endpoint), new DefaultAzureCredential());
+
+IChatClient chatClient = projectClient.ProjectOpenAIClient
+                                      .GetChatClient(deploymentName)
+                                      .AsIChatClient();
+
+Workflow workflow = CreateWorkflow(chatClient);
+
+await RunWorkflowAsync(workflow).ConfigureAwait(false);
+
+static Workflow CreateWorkflow(IChatClient chatClient)
+{
+    AgentRegistry agents = new(chatClient);
+
+    HandoffWorkflowBuilder handoffBuilder = AgentWorkflowBuilder.CreateHandoffBuilderWith(agents.IntakeAgent);
+
+    // Add a handoff to each of the experts from every agent in the registry (experts + Intake)
+    foreach (AIAgent expert in agents.Experts)
+    {
+        handoffBuilder.WithHandoffs(agents.All.Except([expert]), expert);
+    }
+
+    // Let agents request more user information and return to the asking agent (rather than going back to the intake agent)
+    handoffBuilder.EnableReturnToPrevious();
+
+    return handoffBuilder.Build();
+}
+
+static async Task RunWorkflowAsync(Workflow workflow)
+{
+    using CancellationTokenSource cts = CreateConsoleCancelKeySource();
+    await using StreamingRun run = await InProcessExecution.OpenStreamingAsync(workflow, cancellationToken: cts.Token)
+                                                           .ConfigureAwait(false);
+
+    bool hadError = false;
+    do
+    {
+        Console.Write("> ");
+        string userInput = Console.ReadLine() ?? string.Empty;
+
+        if (userInput.Equals("exit", StringComparison.OrdinalIgnoreCase))
+        {
+            break;
+        }
+
+        await run.TrySendMessageAsync(userInput);
+        string? speakingAgent = null;
+        await foreach (WorkflowEvent evt in run.WatchStreamAsync(cts.Token).WithCancellation(cts.Token))
+        {
+            switch (evt)
+            {
+                case AgentResponseUpdateEvent update:
+                {
+                    if (speakingAgent == null || speakingAgent != update.Update.AuthorName)
+                    {
+                        speakingAgent = update.Update.AuthorName;
+                        Console.Write($"\n{speakingAgent}: ");
+                    }
+
+                    Console.Write(update.Update.Text);
+                    break;
+                }
+
+                case WorkflowErrorEvent workflowError:
+                {
+                    Console.ForegroundColor = ConsoleColor.Red;
+
+                    if (workflowError.Exception != null)
+                    {
+                        Console.WriteLine($"\nWorkflow error: {workflowError.Exception}");
+                    }
+                    else
+                    {
+                        Console.WriteLine("\nUnknown workflow error occurred.");
+                    }
+
+                    Console.ResetColor();
+
+                    hadError = true;
+                    break;
+                }
+
+                case WorkflowWarningEvent workflowWarning when workflowWarning.Data is string message:
+                {
+                    Console.ForegroundColor = ConsoleColor.Yellow;
+                    Console.WriteLine(message);
+                    Console.ResetColor();
+                    break;
+                }
+            }
+        }
+    } while (!hadError);
+}
+
+static CancellationTokenSource CreateConsoleCancelKeySource()
+{
+    CancellationTokenSource cts = new();
+
+    // Normally, support a way to detach events, but in this case this is a termination signal, so cleanup will happen
+    // as part of application shutdown.
+    Console.CancelKeyPress += (s, args) =>
+    {
+        cts.Cancel();
+
+        // We handle cleanup + termination ourselves
+        args.Cancel = true;
+    };
+
+    return cts;
+}