.NET: Add missing Azure OpenAI Migration Sample code (#559)

* Add missing Azure OpenAI Migration Sample code

* Add Azure OpenAI Assistants Samples

* Address miner README typos

* Remove leftover

dotnet/samples/SemanticKernelMigration/AzureOpenAI/Step02_ToolCall/Program.cs

@@ -0,0 +1,54 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.ComponentModel;
+using Azure.AI.OpenAI;
+using Azure.Identity;
+using Microsoft.Extensions.AI;
+using Microsoft.SemanticKernel;
+using Microsoft.SemanticKernel.Agents;
+using OpenAI;
+
+var endpoint = Environment.GetEnvironmentVariable("AZUREOPENAI_ENDPOINT") ?? throw new InvalidOperationException("AZUREOPENAI_ENDPOINT is not set.");
+var deploymentName = System.Environment.GetEnvironmentVariable("AZUREOPENAI_DEPLOYMENT_NAME") ?? "gpt-4o";
+var userInput = "What is the weather like in Amsterdam?";
+
+Console.WriteLine($"User Input: {userInput}");
+
+[KernelFunction]
+[Description("Get the weather for a given location.")]
+static string GetWeather([Description("The location to get the weather for.")] string location)
+    => $"The weather in {location} is cloudy with a high of 15°C.";
+
+await SKAgent();
+await AFAgent();
+
+async Task SKAgent()
+{
+    var builder = Kernel.CreateBuilder().AddAzureOpenAIChatClient(deploymentName, endpoint, new AzureCliCredential());
+
+    ChatCompletionAgent agent = new()
+    {
+        Instructions = "You are a helpful assistant",
+        Kernel = builder.Build(),
+        Arguments = new KernelArguments(new PromptExecutionSettings() { FunctionChoiceBehavior = FunctionChoiceBehavior.Auto() }),
+    };
+
+    // Initialize plugin and add to the agent's Kernel (same as direct Kernel usage).
+    agent.Kernel.Plugins.Add(KernelPluginFactory.CreateFromFunctions("KernelPluginName", [KernelFunctionFactory.CreateFromMethod(GetWeather)]));
+
+    Console.WriteLine("\n=== SK Agent Response ===\n");
+
+    var result = await agent.InvokeAsync(userInput).FirstAsync();
+    Console.WriteLine(result.Message);
+}
+
+async Task AFAgent()
+{
+    var agent = new AzureOpenAIClient(new Uri(endpoint), new AzureCliCredential()).GetChatClient(deploymentName)
+        .CreateAIAgent(instructions: "You are a helpful assistant", tools: [AIFunctionFactory.Create(GetWeather)]);
+
+    Console.WriteLine("\n=== AF Agent Response ===\n");
+
+    var result = await agent.RunAsync(userInput);
+    Console.WriteLine(result);
+}