.Net: Create sample showing how to render ChatHistory to a prompt and…

… invoke it (#8899)

### Motivation and Context

Closes #8861 

### Description

<!-- Describe your changes, the overall approach, the underlying design.
These notes will help understanding how your code works. Thanks! -->

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

dotnet/samples/Concepts/PromptTemplates/ChatLoopWithPrompt.cs

@@ -0,0 +1,64 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Microsoft.SemanticKernel;
+using Microsoft.SemanticKernel.ChatCompletion;
+using Microsoft.SemanticKernel.PromptTemplates.Handlebars;
+
+namespace PromptTemplates;
+
+public sealed class ChatLoopWithPrompt(ITestOutputHelper output) : BaseTest(output)
+{
+    /// <summary>
+    /// This sample demonstrates how to render a chat history to a
+    /// prompt and use chat completion prompts in a loop.
+    /// </summary>
+    [Fact]
+    public async Task ExecuteChatLoopAsPromptAsync()
+    {
+        var kernel = Kernel.CreateBuilder()
+            .AddOpenAIChatCompletion(
+                modelId: TestConfiguration.OpenAI.ChatModelId,
+                apiKey: TestConfiguration.OpenAI.ApiKey)
+            .Build();
+
+        var chatHistory = new ChatHistory();
+        KernelArguments arguments = new() { { "chatHistory", chatHistory } };
+
+        string[] userMessages = [
+            "What is Seattle?",
+            "What is the population of Seattle?",
+            "What is the area of Seattle?",
+            "What is the weather in Seattle?",
+            "What is the zip code of Seattle?",
+            "What is the elevation of Seattle?",
+            "What is the latitude of Seattle?",
+            "What is the longitude of Seattle?",
+            "What is the mayor of Seattle?"
+        ];
+
+        foreach (var userMessage in userMessages)
+        {
+            chatHistory.AddUserMessage(userMessage);
+            OutputLastMessage(chatHistory);
+
+            var function = kernel.CreateFunctionFromPrompt(
+                new()
+                {
+                    Template =
+                    """
+                    {{#each (chatHistory)}}
+                    <message role="{{Role}}">{{Content}}</message>
+                    {{/each}}
+                    """,
+                    TemplateFormat = "handlebars"
+                },
+                new HandlebarsPromptTemplateFactory()
+            );
+
+            var response = await kernel.InvokeAsync(function, arguments);
+
+            chatHistory.AddAssistantMessage(response.ToString());
+            OutputLastMessage(chatHistory);
+        }
+    }
+}

dotnet/samples/Concepts/ChatPrompts/SafeChatPrompts.cs → dotnet/samples/Concepts/PromptTemplates/SafeChatPrompts.cs

@@ -2,7 +2,7 @@
 
 using Microsoft.SemanticKernel;
 
-namespace ChatPrompts;
+namespace PromptTemplates;
 
 public sealed class SafeChatPrompts : BaseTest, IDisposable
 {

dotnet/samples/Concepts/README.md

@@ -163,6 +163,8 @@ dotnet test -l "console;verbosity=detailed" --filter "FullyQualifiedName=ChatCom
 - [TemplateLanguage](https://github.com/microsoft/semantic-kernel/blob/main/dotnet/samples/Concepts/PromptTemplates/TemplateLanguage.cs)
 - [PromptyFunction](https://github.com/microsoft/semantic-kernel/blob/main/dotnet/samples/Concepts/PromptTemplates/PromptyFunction.cs)
 - [HandlebarsVisionPrompts](https://github.com/microsoft/semantic-kernel/blob/main/dotnet/samples/Concepts/PromptTemplates/HandlebarsVisionPrompts.cs)
+- [SafeChatPrompts](https://github.com/microsoft/semantic-kernel/blob/main/dotnet/samples/Concepts/PromptTemplates/SafeChatPrompts.cs)
+- [ChatLoopWithPrompt](https://github.com/microsoft/semantic-kernel/blob/main/dotnet/samples/Concepts/PromptTemplates/ChatLoopWithPrompt.cs)
 
 ### RAG - Retrieval-Augmented Generation