OpenAI Assistants Streaming in C#

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

Program.cs
OpenAIAssistantsStreamingClass.cs

How to generate this sample

Command

ai dev new openai-asst-streaming --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-asst-streaming' in 'openai-asst-streaming-cs' (3 files)...

OpenAIAssistantsStreaming.csproj
OpenAIAssistantsStreamingClass.cs
Program.cs

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

Program.cs

STEP 1: Read the configuration settings from environment variables:

Program.cs

var assistantId = Environment.GetEnvironmentVariable("ASSISTANT_ID") ?? "<insert your OpenAI assistant ID here>";
var threadId = args.Length > 0 ? args[0] : null;

// Validate environment variables
var openAIAPIKey = Environment.GetEnvironmentVariable("AZURE_OPENAI_API_KEY") ?? "<insert your Azure OpenAI API key here>";
var openAIEndpoint = Environment.GetEnvironmentVariable("AZURE_OPENAI_ENDPOINT") ?? "<insert your Azure OpenAI endpoint here>";

if (string.IsNullOrEmpty(openAIAPIKey) || openAIAPIKey.StartsWith("<insert") ||
    string.IsNullOrEmpty(openAIEndpoint) || openAIEndpoint.StartsWith("<insert") ||
    string.IsNullOrEmpty(assistantId) || assistantId.StartsWith("<insert"))
{
    Console.WriteLine("To use Azure OpenAI, set the following environment variables:");
    Console.WriteLine("  ASSISTANT_ID\n  AZURE_OPENAI_API_KEY\n  AZURE_OPENAI_ENDPOINT");
    Environment.Exit(1);
}

STEP 2: Initialize the OpenAI client and the assistant:

Program.cs

var client = string.IsNullOrEmpty(openAIAPIKey)
    ? new AzureOpenAIClient(new Uri(openAIEndpoint), new DefaultAzureCredential())
    : new AzureOpenAIClient(new Uri(openAIEndpoint), new AzureKeyCredential(openAIAPIKey));

var assistant = new OpenAIAssistantsStreamingClass(client, assistantId);

STEP 3: Create or retrieve a thread and get thread messages if thread ID is provided:

Program.cs

if (string.IsNullOrEmpty(threadId))
{
    await assistant.CreateThreadAsync();
}
else
{
    await assistant.RetrieveThreadAsync(threadId);
    await assistant.GetThreadMessagesAsync((role, content) => 
    {
        Console.WriteLine($"{char.ToUpper(role[0]) + role.Substring(1)}: {content}\n");
    });
}

STEP 4: Implement the user interaction loop to get responses from the assistant:

Program.cs

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

    Console.Write("\nAssistant: ");
    await assistant.GetResponseAsync(userPrompt, content => {
        Console.Write(content);
    });
}

Console.WriteLine($"Bye! (ThreadId: {assistant.Thread?.Id})");

OpenAIAssistantsStreamingClass.cs

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

OpenAIAssistantsStreamingClass.cs

public OpenAIAssistantsStreamingClass(OpenAIClient client, string assistantId)
{
    _assistantClient = client.GetAssistantClient();
    _assistantId = assistantId;
}

public async Task CreateThreadAsync()
{
    var result = await _assistantClient.CreateThreadAsync();
    Thread = result.Value;
}

public async Task RetrieveThreadAsync(string threadId)
{
    var result = await _assistantClient.GetThreadAsync(threadId);
    Thread = result.Value;
}

public async Task GetThreadMessagesAsync(Action<string, string> callback)
{
    await foreach (var message in _assistantClient.GetMessagesAsync(Thread, ListOrder.OldestFirst))
    {
        var content = string.Join("", message.Content.Select(c => c.Text));
        var role = message.Role == MessageRole.User ? "user" : "assistant";
        callback(role, content);
    }
}

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

OpenAIAssistantsStreamingClass.cs

public async Task GetResponseAsync(string userInput, Action<string> callback)
{
    await _assistantClient.CreateMessageAsync(Thread, [ userInput ]);
    var assistant = await _assistantClient.GetAssistantAsync(_assistantId);
    var stream = _assistantClient.CreateRunStreamingAsync(Thread, assistant.Value);

STEP 3: Send the chat message history to the streaming OpenAI Assistants API and process each update:

OpenAIAssistantsStreamingClass.cs

    await foreach (var update in stream) 
    {
        if (update is MessageContentUpdate contentUpdate)
        {
            callback(contentUpdate.Text);
        }

        if (update.UpdateKind == StreamingUpdateReason.RunStepCompleted)
        {
            callback("\n\n");
        }
    }
}