.Net: Visualizing dotnet workflows (#882)

* Adding more test for workflow vizualization.

* Improving README for sample.

* More cleanup.

* Removing rendering of workflow visualization and adding basic support for mermaid format.

* Adding basic mermaid tests.

* Improving sample. Switching to another branch.

* About to merge from main.

* Formatting.

* More fromatting.

* Removng uneeded call to ToUpper.

* Adding README.

* Moving samples under workflow to workflows.

* Removing uneeded README for map-reduce sample.

dotnet/samples/GettingStarted/Workflows/Visualization/Program.cs

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+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using Microsoft.Agents.AI.Workflows;
+
+namespace WorkflowVisualizationSample;
+
+/// <summary>
+/// Sample demonstrating workflow visualization using Mermaid and DOT (Graphviz) formats.
+/// </summary>
+/// <remarks>
+/// This sample shows how to use the ToMermaidString() and ToDotString() extension methods
+/// to generate visual representations of workflow graphs. The visualizations can be used
+/// for documentation, debugging, and understanding complex workflow structures.
+/// </remarks>
+internal static class Program
+{
+    /// <summary>
+    /// Entry point that generates and displays workflow visualizations in Mermaid and DOT formats.
+    /// </summary>
+    /// <param name="args">Command line arguments (not used).</param>
+    private static void Main(string[] args)
+    {
+        // Step 1: Build the workflow you want to visualize
+        Workflow workflow = WorkflowMapReduceSample.Program.BuildWorkflow();
+
+        // Step 2: Generate and display workflow visualization
+        Console.WriteLine("Generating workflow visualization...");
+
+        // Mermaid
+        Console.WriteLine("Mermaid string: \n=======");
+        var mermaid = workflow.ToMermaidString();
+        Console.WriteLine(mermaid);
+        Console.WriteLine("=======");
+
+        // DOT
+        Console.WriteLine("DiGraph string: *** Tip: To export DOT as an image, install Graphviz and pipe the DOT output to 'dot -Tsvg', 'dot -Tpng', etc. *** \n=======");
+        var dotString = workflow.ToDotString();
+        Console.WriteLine(dotString);
+        Console.WriteLine("=======");
+    }
+}

dotnet/samples/GettingStarted/Workflows/Visualization/README.md

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+# Workflow Visualization Sample
+
+This sample demonstrates how to visualize workflows using `ToMermaidString()` and `ToDotString()` extension methods. It uses a map-reduce workflow with fan-out/fan-in patterns as an example.
+
+## Running the Sample
+
+```bash
+dotnet run
+```
+
+## Output Formats
+
+The sample generates two visualization formats:
+
+### Mermaid
+Paste the output into any Mermaid-compatible viewer (GitHub, Mermaid Live Editor, etc.):
+
+![Mermaid Visualization](Resources/mermaid_render.png)
+
+### DOT (Graphviz)
+Render with Graphviz (requires `graphviz` to be installed):
+
+```bash
+dotnet run | tail -n +20 | dot -Tpng -o workflow.png
+```
+
+![Graphviz Visualization](Resources/graphviz_render.png)
+
+## Usage
+
+```csharp
+Workflow workflow = BuildWorkflow();
+
+// Generate Mermaid format
+string mermaid = workflow.ToMermaidString();
+
+// Generate DOT format
+string dotString = workflow.ToDotString();
+```
+
+## Related Samples
+
+- [Map-Reduce Workflow Sample](../../../Workflows/Visualization/README.md): The workflow implementation being visualized

dotnet/samples/GettingStarted/Workflows/Visualization/Visualization.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net9.0</TargetFramework>
+
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>disable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\..\src\Microsoft.Agents.AI.Workflows\Microsoft.Agents.AI.Workflows.csproj" />
+    <ProjectReference Include="..\Concurrent\MapReduce\MapReduce.csproj" />
+  </ItemGroup>
+
+</Project>