OpenAI Chat API in C#

This sample demonstrates how to use the OpenAI Chat API in a C# console application.

Program.cs
OpenAIChatCompletionsClass.cs

How to generate this sample

Command

ai dev new openai-chat --csharp

Output

AI - Azure AI CLI, Version 1.0.0
Copyright (c) 2024 Microsoft Corporation. All Rights Reserved.

This PUBLIC PREVIEW version may change at any time.
See: https://aka.ms/azure-ai-cli-public-preview

Generating 'openai-chat' in 'openai-chat-cs' (3 files)...

OpenAIChatCompletions.csproj
OpenAIChatCompletionsClass.cs
Program.cs

Generating 'openai-chat' in 'openai-chat-cs' (3 files)... DONE!

Program.cs

STEP 1: Read the configuration settings from environment variables.

Program.cs

var openAIAPIKey = Environment.GetEnvironmentVariable("AZURE_OPENAI_API_KEY") ?? "<insert your OpenAI API key here>";
var openAIEndpoint = Environment.GetEnvironmentVariable("AZURE_OPENAI_ENDPOINT") ?? "<insert your OpenAI endpoint here>";
var openAIChatDeploymentName = Environment.GetEnvironmentVariable("AZURE_OPENAI_CHAT_DEPLOYMENT") ?? "<insert your OpenAI chat deployment name here>";
var openAISystemPrompt = Environment.GetEnvironmentVariable("AZURE_OPENAI_SYSTEM_PROMPT") ?? "You are a helpful AI assistant.";

STEP 2: Initialize the helper class with the configuration settings.

Program.cs

var chat = new OpenAIChatCompletionsClass(openAIEndpoint, openAIAPIKey, openAIChatDeploymentName, openAISystemPrompt);

STEP 3: Obtain user input, use the helper class to get the assistant's response, and display the response.

Program.cs

while (true)
{
    Console.Write("User: ");
    var userPrompt = Console.ReadLine();
    if (string.IsNullOrEmpty(userPrompt) || userPrompt == "exit") break;

    var response = chat.GetChatCompletion(userPrompt);
    Console.WriteLine($"\nAssistant: {response}\n");
}

OpenAIChatCompletionsClass.cs

STEP 1: Create the client and initialize chat message history with a system message.

OpenAIChatCompletionsClass.cs

public OpenAIChatCompletionsClass(string openAIEndpoint, string openAIAPIKey, string openAIChatDeploymentName, string openAISystemPrompt)
{
    _openAISystemPrompt = openAISystemPrompt;

    _client = string.IsNullOrEmpty(openAIAPIKey)
        ? new AzureOpenAIClient(new Uri(openAIEndpoint), new DefaultAzureCredential())
        : new AzureOpenAIClient(new Uri(openAIEndpoint), new AzureKeyCredential(openAIAPIKey));
    _chatClient = _client.GetChatClient(openAIChatDeploymentName);
    _messages = new List<ChatMessage>();

    ClearConversation();
}

public void ClearConversation()
{
    _messages.Clear();
    _messages.Add(ChatMessage.CreateSystemMessage(_openAISystemPrompt));
}

STEP 2: When the user provides input, add the user message to the chat message history.

OpenAIChatCompletionsClass.cs

public string GetChatCompletion(string userPrompt)
{
    _messages.Add(ChatMessage.CreateUserMessage(userPrompt));

STEP 3: Send the chat message history to the OpenAI Chat API and process the response.

OpenAIChatCompletionsClass.cs

    var response = _chatClient.CompleteChat(_messages);
    var responseText = string.Join("", response.Value.Content
        .Where(x => x.Kind == ChatMessageContentPartKind.Text)
        .Select(x => x.Text)
        .ToList());

STEP 4: Add the assistant's response to the chat message history and return the response.

OpenAIChatCompletionsClass.cs

    _messages.Add(ChatMessage.CreateAssistantMessage(responseText));
    return responseText;
}