docs: add .NET example for weather assistant using Copilot SDK

Author: vicperdana

docs/getting-started.md

@@ -779,6 +779,74 @@ python weather_assistant.py
 
 </details>
 
+<details>
+<summary><strong>.NET</strong></summary>
+
+Create a new console project and update `Program.cs`:
+
+```csharp
+using GitHub.Copilot.SDK;
+using Microsoft.Extensions.AI;
+using System.ComponentModel;
+
+// Define the weather tool using AIFunctionFactory
+var getWeather = AIFunctionFactory.Create(
+    ([Description("The city name")] string city) =>
+    {
+        var conditions = new[] { "sunny", "cloudy", "rainy", "partly cloudy" };
+        var random = new Random();
+        var temp = random.Next(50, 80);
+        var condition = conditions[random.Next(conditions.Length)];
+        return new { city, temperature = $"{temp}°F", condition };
+    },
+    "get_weather",
+    "Get the current weather for a city");
+
+await using var client = new CopilotClient();
+await using var session = await client.CreateSessionAsync(new SessionConfig
+{
+    Model = "gpt-4.1",
+    Streaming = true,
+    Tools = [getWeather]
+});
+
+// Listen for response chunks
+session.On(ev =>
+{
+    if (ev is AssistantMessageDeltaEvent deltaEvent)
+    {
+        Console.Write(deltaEvent.Data.DeltaContent);
+    }
+});
+
+Console.WriteLine("🌤️  Weather Assistant (type 'exit' to quit)");
+Console.WriteLine("   Try: 'What's the weather in Paris?' or 'Compare weather in NYC and LA'\n");
+
+while (true)
+{
+    Console.Write("You: ");
+    var input = Console.ReadLine();
+
+    if (string.IsNullOrEmpty(input) || input.Equals("exit", StringComparison.OrdinalIgnoreCase))
+    {
+        break;
+    }
+
+    Console.Write("Assistant: ");
+    await session.SendAndWaitAsync(new MessageOptions { Prompt = input });
+    Console.WriteLine("\n");
+}
+```
+
+Run with:
+
+```bash
+dotnet run
+```
+
+</details>
+
+
 **Example session:**
 
 ```