How to use generative AI in .NET 10

using Microsoft.Extensions.AI;
using OpenAI;
var builder = WebApplication.CreateBuilder(args); 
var apiKey = builder.Configuration["OpenAI:ApiKey"];
if (string.IsNullOrEmpty(apiKey))
{
    throw new InvalidOperationException("OpenAI API key is missing. Add it to appsettings.json (OpenAI:ApiKey), set environment variable OpenAI__ApiKey, or use user-secrets.");
}
var model = builder.Configuration["OpenAI:Model"] ?? throw new InvalidOperationException("OpenAI model is missing.");

IChatClient openAiChatClient = new OpenAIClient(apiKey).GetChatClient(model).AsIChatClient();

builder.Services.AddChatClient(openAiChatClient);
var app = builder.Build(); 
app.MapPost("/api/explain", async (CodeRequest request, IChatClient chatClient, CancellationToken cancellationToken) => 
{ 
    if (string.IsNullOrWhiteSpace(request.Code)) 
    { 
        return Results.BadRequest(new { error = "Code is required." });
    } 
    var prompt = $"""
     You are an experienced .NET developer. Explain the following C# code in simple English. Keep your explanation below 100 words. C# Code: 
    {request.Code} 
    """;
    var response = await chatClient.GetResponseAsync(prompt, cancellationToken: cancellationToken); 
    return Results.Ok(new CodeExplanationResponse(response.Text)); 
});
app.Run(); 
public record CodeRequest(string Code);

public record CodeExplanationResponse(string Explanation);