OpenAI API — anropa GPT från C#

using System.Net.Http;
using System.Net.Http.Json;
using System.Text.Json;

public class OpenAiKlient
{
    private readonly HttpClient _http;
    private readonly string     _apiKey;
    private const    string     ApiUrl  = "https://api.openai.com/v1/chat/completions";
    private const    string     Model  = "gpt-4o";

    public OpenAiKlient(string apiKey)
    {
        _apiKey = apiKey;
        _http   = new HttpClient();
        _http.DefaultRequestHeaders.Add("Authorization", $"Bearer {apiKey}");
    }

    public async Task<string> FrågaAsync(string question, string systemPrompt = "")
    {
        var messages = new List<object>();

        if (!string.IsNullOrEmpty(systemPrompt))
            messages.Add(new { role = "system", content = systemPrompt });

        messages.Add(new { role = "user", content = question });

        var request = new
        {
            model       = Model,
            max_tokens  = 1024,
            messages    = messages
        };

        var response = await _http.PostAsJsonAsync(ApiUrl, request);
        response.EnsureSuccessStatusCode();

        var json = await response.Content.ReadAsStringAsync();
        var doc  = JsonDocument.Parse(json);

        return doc.RootElement
                  .GetProperty("choices")[0]
                  .GetProperty("message")
                  .GetProperty("content")
                  .GetString() ?? "";
    }
}

var apiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY")
    ?? throw new InvalidOperationException("OPENAI_API_KEY saknas");

var gpt = new OpenAiKlient(apiKey);

string answer = await gpt.FrågaAsync(
    question:        "Förklara skillnaden mellan value types och reference types i C#",
    systemPrompt: "Du är en C#-lärare. Svara kortfattat på svenska."
);

Console.WriteLine(answer);

using OpenAI;
using OpenAI.Chat;

var client = new ChatClient("gpt-4o", apiKey);
var answer   = await client.CompleteChatAsync("Förklara async/await");

Console.WriteLine(answer.Value.Content[0].Text);