Integrating Open AI Chat completion in .NET Core 8 Web API

IChatCompletionServic.cs

namespace OpenAI_ChatGPT
{
    public interface IChatCompletionService
    {
        Task<string> GetChatCompletionAsync(string question);
    }
}

Create the Models for ChatCompletionRequest and ChatCompletionResponse.

using System.Text.Json.Serialization;

namespace OpenAI_ChatGPT
{
    public class ChatCompletionRequest
    {
        [JsonPropertyName("model")]
        public string Model { get; set; }
        [JsonPropertyName("messages")]
        public List<Message> Messages { get; set; }
        [JsonPropertyName("max_tokens")]
        public int MaxTokens { get; set; }

    }

    public class Choice
    {
        [JsonPropertyName("index")]
        public int Index { get; set; }

        [JsonPropertyName("message")]
        public Message Message { get; set; }

        [JsonPropertyName("logprobs")]
        public object Logprobs { get; set; }

        [JsonPropertyName("finish_reason")]
        public string FinishReason { get; set; }
    }

    public class Message
    {
        [JsonPropertyName("role")]
        public string Role { get; set; }

        [JsonPropertyName("content")]
        public string Content { get; set; }
    }

    public class ChatCompletionResponse
    {
        [JsonPropertyName("id")]
        public string Id { get; set; }

        [JsonPropertyName("object")]
        public string Object { get; set; }

        [JsonPropertyName("created")]
        public int Created { get; set; }

        [JsonPropertyName("model")]
        public string Model { get; set; }

        [JsonPropertyName("choices")]
        public List<Choice> Choices { get; set; }

        [JsonPropertyName("usage")]
        public Usage Usage { get; set; }

        [JsonPropertyName("system_fingerprint")]
        public object SystemFingerprint { get; set; }
    }

    public class Usage
    {
        [JsonPropertyName("prompt_tokens")]
        public int PromptTokens { get; set; }

        [JsonPropertyName("completion_tokens")]
        public int CompletionTokens { get; set; }

        [JsonPropertyName("total_tokens")]
        public int TotalTokens { get; set; }
    }
}

Register the dependency in the Program.cs.

builder.Services.AddHttpClient(); // Adds the IHttpClientFactory and related services to service coll

builder.Services.AddScoped<IChatCompletionService, ChatCompletionService>();

Now create the controller and inject the ChatCompletionService to consume the API.

using Microsoft.AspNetCore.Mvc;

namespace OpenAI_ChatGPT.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class ChatCompletionController(IChatCompletionService chatCompletionService) : ControllerBase
    {

        [HttpGet("answer")]
        public async Task<IActionResult> Get(string question)
        {
            var response = await chatCompletionService.GetChatCompletionAsync(question);
            return Ok(response);
        }
    }
}

We are done with our all code changes now let's run the application and ask some interesting questions.

Awesome, here we can see we are getting the response based on our question.

All the code used in this article is available in the Github repository: https://github.com/rahulsdotnet/OpenAI_ChatGPT

I hope you enjoyed this article, Happy Coding!!