.NET: [Feature Branch] Add nested sub-workflow support for durable workflows

dotnet/agent-framework-dotnet.slnx

@@ -54,6 +54,7 @@
     <Project Path="samples/Durable/Workflow/ConsoleApps/04_WorkflowAndAgents/04_WorkflowAndAgents.csproj" />
     <Project Path="samples/Durable/Workflow/ConsoleApps/05_WorkflowEvents/05_WorkflowEvents.csproj" />
     <Project Path="samples/Durable/Workflow/ConsoleApps/06_WorkflowSharedState/06_WorkflowSharedState.csproj" />
+    <Project Path="samples/Durable/Workflow/ConsoleApps/07_SubWorkflows/07_SubWorkflows.csproj" />
   </Folder>
   <Folder Name="/Samples/Durable/Workflows/AzureFunctions/">
     <Project Path="samples/Durable/Workflow/AzureFunctions/01_SequentialWorkflow/01_SequentialWorkflow.csproj" />

dotnet/samples/Durable/Workflow/ConsoleApps/07_SubWorkflows/07_SubWorkflows.csproj

@@ -0,0 +1,28 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFrameworks>net10.0</TargetFrameworks>
+    <OutputType>Exe</OutputType>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <AssemblyName>SubWorkflows</AssemblyName>
+    <RootNamespace>SubWorkflows</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Azure.Identity" />
+    <PackageReference Include="Microsoft.DurableTask.Client.AzureManaged" />
+    <PackageReference Include="Microsoft.DurableTask.Worker.AzureManaged" />
+    <PackageReference Include="Microsoft.Extensions.Hosting" />
+  </ItemGroup>
+
+  <!-- Local projects that should be switched to package references when using the sample outside of this MAF repo -->
+  <!--
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Agents.AI.DurableTask" />
+    <PackageReference Include="Microsoft.Agents.AI.Workflows" />
+  </ItemGroup>
+  -->
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\..\..\src\Microsoft.Agents.AI.DurableTask\Microsoft.Agents.AI.DurableTask.csproj" />
+  </ItemGroup>
+</Project>

dotnet/samples/Durable/Workflow/ConsoleApps/07_SubWorkflows/Executors.cs

@@ -0,0 +1,233 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Microsoft.Agents.AI.Workflows;
+using Microsoft.Agents.AI.Workflows.Checkpointing;
+
+namespace SubWorkflows;
+
+/// <summary>
+/// Event emitted when the fraud check risk score is calculated.
+/// </summary>
+internal sealed class FraudRiskAssessedEvent(int riskScore) : WorkflowEvent($"Risk score: {riskScore}/100")
+{
+    public int RiskScore => riskScore;
+}
+
+/// <summary>
+/// Represents an order being processed through the workflow.
+/// </summary>
+internal sealed class OrderInfo
+{
+    public required string OrderId { get; set; }
+
+    public decimal Amount { get; set; }
+
+    public string? PaymentTransactionId { get; set; }
+
+    public string? TrackingNumber { get; set; }
+
+    public string? Carrier { get; set; }
+}
+
+// Main workflow executors
+
+/// <summary>
+/// Entry point executor that receives the order ID and creates an OrderInfo object.
+/// </summary>
+internal sealed class OrderReceived() : Executor<string, OrderInfo>("OrderReceived")
+{
+    public override ValueTask<OrderInfo> HandleAsync(string message, IWorkflowContext context, CancellationToken cancellationToken = default)
+    {
+        Console.WriteLine();
+        Console.ForegroundColor = ConsoleColor.Cyan;
+        Console.WriteLine($"[OrderReceived] Processing order '{message}'");
+        Console.ResetColor();
+
+        OrderInfo order = new()
+        {
+            OrderId = message,
+            Amount = 99.99m // Simulated order amount
+        };
+
+        return ValueTask.FromResult(order);
+    }
+}
+
+/// <summary>
+/// Final executor that outputs the completed order summary.
+/// </summary>
+internal sealed class OrderCompleted() : Executor<OrderInfo, string>("OrderCompleted")
+{
+    public override ValueTask<string> HandleAsync(OrderInfo message, IWorkflowContext context, CancellationToken cancellationToken = default)
+    {
+        Console.WriteLine();
+        Console.ForegroundColor = ConsoleColor.Green;
+        Console.WriteLine("┌─────────────────────────────────────────────────────────────────┐");
+        Console.WriteLine($"│ [OrderCompleted] Order '{message.OrderId}' successfully processed!");
+        Console.WriteLine($"│   Payment: {message.PaymentTransactionId}");
+        Console.WriteLine($"│   Shipping: {message.Carrier} - {message.TrackingNumber}");
+        Console.WriteLine("└─────────────────────────────────────────────────────────────────┘");
+        Console.ResetColor();
+
+        return ValueTask.FromResult($"Order {message.OrderId} completed. Tracking: {message.TrackingNumber}");
+    }
+}
+
+// Payment sub-workflow executors
+
+/// <summary>
+/// Validates payment information for an order.
+/// </summary>
+internal sealed class ValidatePayment() : Executor<OrderInfo, OrderInfo>("ValidatePayment")
+{
+    public override async ValueTask<OrderInfo> HandleAsync(OrderInfo message, IWorkflowContext context, CancellationToken cancellationToken = default)
+    {
+        Console.WriteLine();
+        Console.ForegroundColor = ConsoleColor.Yellow;
+        Console.WriteLine($"  [Payment/ValidatePayment] Validating payment for order '{message.OrderId}'...");
+        Console.ResetColor();
+
+        await Task.Delay(TimeSpan.FromMilliseconds(100), cancellationToken);
+
+        Console.ForegroundColor = ConsoleColor.Yellow;
+        Console.WriteLine($"  [Payment/ValidatePayment] Payment validated for ${message.Amount}");
+        Console.ResetColor();
+
+        return message;
+    }
+}
+
+/// <summary>
+/// Charges the payment for an order.
+/// </summary>
+internal sealed class ChargePayment() : Executor<OrderInfo, OrderInfo>("ChargePayment")
+{
+    public override async ValueTask<OrderInfo> HandleAsync(OrderInfo message, IWorkflowContext context, CancellationToken cancellationToken = default)
+    {
+        Console.ForegroundColor = ConsoleColor.Yellow;
+        Console.WriteLine($"  [Payment/ChargePayment] Charging ${message.Amount} for order '{message.OrderId}'...");
+        Console.ResetColor();
+
+        await Task.Delay(TimeSpan.FromMilliseconds(100), cancellationToken);
+
+        message.PaymentTransactionId = $"TXN-{Guid.NewGuid().ToString("N")[..8].ToUpperInvariant()}";
+
+        Console.ForegroundColor = ConsoleColor.Yellow;
+        Console.WriteLine($"  [Payment/ChargePayment] ✓ Payment processed: {message.PaymentTransactionId}");
+        Console.ResetColor();
+
+        return message;
+    }
+}
+
+// FraudCheck sub-sub-workflow executors (nested inside Payment)
+
+/// <summary>
+/// Analyzes transaction patterns for potential fraud.
+/// </summary>
+internal sealed class AnalyzePatterns() : Executor<OrderInfo, OrderInfo>("AnalyzePatterns")
+{
+    public override async ValueTask<OrderInfo> HandleAsync(OrderInfo message, IWorkflowContext context, CancellationToken cancellationToken = default)
+    {
+        Console.ForegroundColor = ConsoleColor.DarkYellow;
+        Console.WriteLine($"    [Payment/FraudCheck/AnalyzePatterns] Analyzing patterns for order '{message.OrderId}'...");
+        Console.ResetColor();
+
+        await Task.Delay(TimeSpan.FromMilliseconds(100), cancellationToken);
+
+        // Store analysis results in shared state for the next executor in this sub-workflow
+        int patternsFound = new Random().Next(0, 5);
+        await context.QueueStateUpdateAsync("patternsFound", patternsFound, cancellationToken: cancellationToken);
+
+        Console.ForegroundColor = ConsoleColor.DarkYellow;
+        Console.WriteLine($"    [Payment/FraudCheck/AnalyzePatterns] ✓ Pattern analysis complete ({patternsFound} suspicious patterns)");
+        Console.ResetColor();
+
+        return message;
+    }
+}
+
+/// <summary>
+/// Calculates a risk score for the transaction.
+/// </summary>
+internal sealed class CalculateRiskScore() : Executor<OrderInfo, OrderInfo>("CalculateRiskScore")
+{
+    public override async ValueTask<OrderInfo> HandleAsync(OrderInfo message, IWorkflowContext context, CancellationToken cancellationToken = default)
+    {
+        Console.ForegroundColor = ConsoleColor.DarkYellow;
+        Console.WriteLine($"    [Payment/FraudCheck/CalculateRiskScore] Calculating risk score for order '{message.OrderId}'...");
+        Console.ResetColor();
+
+        await Task.Delay(TimeSpan.FromMilliseconds(100), cancellationToken);
+
+        // Read the pattern count from shared state (written by AnalyzePatterns)
+        int patternsFound = await context.ReadStateAsync<int>("patternsFound", cancellationToken: cancellationToken);
+        int riskScore = Math.Min(patternsFound * 20 + new Random().Next(1, 20), 100);
+
+        // Emit a workflow event from within a nested sub-workflow
+        await context.AddEventAsync(new FraudRiskAssessedEvent(riskScore), cancellationToken);
+
+        Console.ForegroundColor = ConsoleColor.DarkYellow;
+        Console.WriteLine($"    [Payment/FraudCheck/CalculateRiskScore] ✓ Risk score: {riskScore}/100 (based on {patternsFound} patterns)");
+        Console.ResetColor();
+
+        return message;
+    }
+}
+
+// Shipping sub-workflow executors
+
+/// <summary>
+/// Selects a shipping carrier for an order.
+/// </summary>
+/// <remarks>
+/// This executor uses <see cref="Executor{TInput}"/> (void return) combined with
+/// <see cref="IWorkflowContext.SendMessageAsync"/> to forward the order to the next
+/// connected executor (CreateShipment). This demonstrates explicit typed message passing
+/// as an alternative to returning a value from the handler.
+/// </remarks>
+internal sealed class SelectCarrier() : Executor<OrderInfo>("SelectCarrier")
+{
+    public override async ValueTask HandleAsync(OrderInfo message, IWorkflowContext context, CancellationToken cancellationToken = default)
+    {
+        Console.WriteLine();
+        Console.ForegroundColor = ConsoleColor.Blue;
+        Console.WriteLine($"  [Shipping/SelectCarrier] Selecting carrier for order '{message.OrderId}'...");
+        Console.ResetColor();
+
+        await Task.Delay(TimeSpan.FromMilliseconds(100), cancellationToken);
+
+        message.Carrier = message.Amount > 50 ? "Express" : "Standard";
+
+        Console.ForegroundColor = ConsoleColor.Blue;
+        Console.WriteLine($"  [Shipping/SelectCarrier] ✓ Selected carrier: {message.Carrier}");
+        Console.ResetColor();
+
+        // Use SendMessageAsync to forward the updated order to connected executors.
+        // With a void-return executor, this is the mechanism for passing data downstream.
+        await context.SendMessageAsync(message, cancellationToken: cancellationToken);
+    }
+}
+
+/// <summary>
+/// Creates shipment and generates tracking number.
+/// </summary>
+internal sealed class CreateShipment() : Executor<OrderInfo, OrderInfo>("CreateShipment")
+{
+    public override async ValueTask<OrderInfo> HandleAsync(OrderInfo message, IWorkflowContext context, CancellationToken cancellationToken = default)
+    {
+        Console.ForegroundColor = ConsoleColor.Blue;
+        Console.WriteLine($"  [Shipping/CreateShipment] Creating shipment for order '{message.OrderId}'...");
+        Console.ResetColor();
+
+        await Task.Delay(TimeSpan.FromMilliseconds(100), cancellationToken);
+
+        message.TrackingNumber = $"TRACK-{Guid.NewGuid().ToString("N")[..10].ToUpperInvariant()}";
+
+        Console.ForegroundColor = ConsoleColor.Blue;
+        Console.WriteLine($"  [Shipping/CreateShipment] ✓ Shipment created: {message.TrackingNumber}");
+        Console.ResetColor();
+
+        return message;
+    }
+}