Add missing code snippet

Author: justinyoo

03-agentic-design-patterns/code_samples/03-dotnet-agent-framework.md

@@ -161,5 +161,130 @@ dotnet run ./03-dotnet-agent-framework.cs
 See [`03-dotnet-agent-framework.cs`](./03-dotnet-agent-framework.cs) for the complete code.
 
 ```csharp
-
+#!/usr/bin/dotnet run
+
+#:package Microsoft.Extensions.AI@10.*
+#:package Microsoft.Agents.AI.OpenAI@1.*-*
+
+using System.ClientModel;
+using System.ComponentModel;
+
+using Microsoft.Agents.AI;
+using Microsoft.Extensions.AI;
+
+using OpenAI;
+
+// Tool Function: Random Destination Generator
+// This static method will be available to the agent as a callable tool
+// The [Description] attribute helps the AI understand when to use this function
+// This demonstrates how to create custom tools for AI agents
+[Description("Provides a random vacation destination.")]
+static string GetRandomDestination()
+{
+    // List of popular vacation destinations around the world
+    // The agent will randomly select from these options
+    var destinations = new List<string>
+    {
+        "Paris, France",
+        "Tokyo, Japan",
+        "New York City, USA",
+        "Sydney, Australia",
+        "Rome, Italy",
+        "Barcelona, Spain",
+        "Cape Town, South Africa",
+        "Rio de Janeiro, Brazil",
+        "Bangkok, Thailand",
+        "Vancouver, Canada"
+    };
+
+    // Generate random index and return selected destination
+    // Uses System.Random for simple random selection
+    var random = new Random();
+    int index = random.Next(destinations.Count);
+    return destinations[index];
+}
+
+// Extract configuration from environment variables
+// Retrieve the GitHub Models API endpoint, defaults to https://models.github.ai/inference if not specified
+// Retrieve the model ID, defaults to openai/gpt-5-mini if not specified
+// Retrieve the GitHub token for authentication, throws exception if not specified
+var github_endpoint = Environment.GetEnvironmentVariable("GH_ENDPOINT") ?? "https://models.github.ai/inference";
+var github_model_id = Environment.GetEnvironmentVariable("GH_MODEL_ID") ?? "openai/gpt-5-mini";
+var github_token = Environment.GetEnvironmentVariable("GH_TOKEN") ?? throw new InvalidOperationException("GH_TOKEN is not set.");
+
+// Configure OpenAI Client Options
+// Create configuration options to point to GitHub Models endpoint
+// This redirects OpenAI client calls to GitHub's model inference service
+var openAIOptions = new OpenAIClientOptions()
+{
+    Endpoint = new Uri(github_endpoint)
+};
+
+// Initialize OpenAI Client with GitHub Models Configuration
+// Create OpenAI client using GitHub token for authentication
+// Configure it to use GitHub Models endpoint instead of OpenAI directly
+var openAIClient = new OpenAIClient(new ApiKeyCredential(github_token), openAIOptions);
+
+// Define Agent Identity and Comprehensive Instructions
+// Agent name for identification and logging purposes
+var AGENT_NAME = "TravelAgent";
+
+// Detailed instructions that define the agent's personality, capabilities, and behavior
+// This system prompt shapes how the agent responds and interacts with users
+var AGENT_INSTRUCTIONS = """
+You are a helpful AI Agent that can help plan vacations for customers.
+
+Important: When users specify a destination, always plan for that location. Only suggest random destinations when the user hasn't specified a preference.
+
+When the conversation begins, introduce yourself with this message:
+"Hello! I'm your TravelAgent assistant. I can help plan vacations and suggest interesting destinations for you. Here are some things you can ask me:
+1. Plan a day trip to a specific location
+2. Suggest a random vacation destination
+3. Find destinations with specific features (beaches, mountains, historical sites, etc.)
+4. Plan an alternative trip if you don't like my first suggestion
+
+What kind of trip would you like me to help you plan today?"
+
+Always prioritize user preferences. If they mention a specific destination like "Bali" or "Paris," focus your planning on that location rather than suggesting alternatives.
+""";
+
+// Create AI Agent with Advanced Travel Planning Capabilities
+// Initialize complete agent pipeline: OpenAI client → Chat client → AI agent
+// Configure agent with name, detailed instructions, and available tools
+// This demonstrates the .NET agent creation pattern with full configuration
+AIAgent agent = openAIClient
+    .GetChatClient(github_model_id)
+    .CreateAIAgent(
+        name: AGENT_NAME,
+        instructions: AGENT_INSTRUCTIONS,
+        tools: [AIFunctionFactory.Create(GetRandomDestination)]
+    );
+
+// Create New Conversation Thread for Context Management
+// Initialize a new conversation thread to maintain context across multiple interactions
+// Threads enable the agent to remember previous exchanges and maintain conversational state
+// This is essential for multi-turn conversations and contextual understanding
+AgentThread thread = agent.GetNewThread();
+
+// Execute Agent: First Travel Planning Request
+// Run the agent with an initial request that will likely trigger the random destination tool
+// The agent will analyze the request, use the GetRandomDestination tool, and create an itinerary
+// Using the thread parameter maintains conversation context for subsequent interactions
+await foreach (var update in agent.RunStreamingAsync("Plan me a day trip", thread))
+{
+    await Task.Delay(10);
+    Console.Write(update);
+}
+
+Console.WriteLine();
+
+// Execute Agent: Follow-up Request with Context Awareness
+// Demonstrate contextual conversation by referencing the previous response
+// The agent remembers the previous destination suggestion and will provide an alternative
+// This showcases the power of conversation threads and contextual understanding in .NET agents
+await foreach (var update in agent.RunStreamingAsync("I don't like that destination. Plan me another vacation.", thread))
+{
+    await Task.Delay(10);
+    Console.Write(update);
+}
 ```