Build an AI chat app with .NET

In this quickstart, you learn how to create a conversational .NET console chat app using an OpenAI or Azure OpenAI model. The app uses the Microsoft.Extensions.AI library so you can write code using AI abstractions rather than a specific SDK. AI abstractions enable you to change the underlying AI model with minimal code changes.

Create the app

Complete the following steps to create a .NET console app to connect to an AI model.

1. In an empty directory on your computer, use the dotnet new command to create a new console app:

   dotnet new console -o ChatAppAI
   

2. Change directory into the app folder:

   cd ChatAppAI
   

3. Install the required packages:

   dotnet add package Azure.Identity
   dotnet add package Azure.AI.OpenAI
   dotnet add package Microsoft.Extensions.AI.OpenAI --prerelease
   dotnet add package Microsoft.Extensions.Configuration
   dotnet add package Microsoft.Extensions.Configuration.UserSecrets
   

   dotnet add package OpenAI
   dotnet add package Microsoft.Extensions.AI.OpenAI --prerelease
   dotnet add package Microsoft.Extensions.Configuration
   dotnet add package Microsoft.Extensions.Configuration.UserSecrets
   

4. Open the app in Visual Studio Code (or your editor of choice).

   code .
   

Add the app code

This app uses the Microsoft.Extensions.AI package to send and receive requests to the AI model. The app provides users with information about hiking trails.

1. In the Program.cs file, add the following code to connect and authenticate to the AI model.

   IConfigurationRoot config = new ConfigurationBuilder().AddUserSecrets<Program>().Build();
   string endpoint = config["AZURE_OPENAI_ENDPOINT"];
   string deployment = config["AZURE_OPENAI_GPT_NAME"];
   
   IChatClient chatClient =
       new AzureOpenAIClient(new Uri(endpoint), new DefaultAzureCredential())
       .GetChatClient(deployment)
       .AsIChatClient();
   

   Note

   DefaultAzureCredential searches for authentication credentials from your local tooling. If you aren't using the azd template to provision the Azure OpenAI resource, you'll need to assign the Azure AI Developer role to the account you used to sign in to Visual Studio or the Azure CLI. For more information, see Authenticate to Azure AI services with .NET.

   var config = new ConfigurationBuilder().AddUserSecrets<Program>().Build();
   string model = config["ModelName"];
   string key = config["OpenAIKey"];
   
   // Create the IChatClient
   IChatClient chatClient =
       new OpenAIClient(key).GetChatClient(model).AsIChatClient();
   

2. Create a system prompt to provide the AI model with initial role context and instructions about hiking recommendations:

   // Start the conversation with context for the AI model
   List<ChatMessage> chatHistory =
       [
           new ChatMessage(ChatRole.System, """
               You are a friendly hiking enthusiast who helps people discover fun hikes in their area.
               You introduce yourself when first saying hello.
               When helping people out, you always ask them for this information
               to inform the hiking recommendation you provide:
   
               1. The ___location where they would like to hike
               2. What hiking intensity they are looking for
   
               You will then provide three suggestions for nearby hikes that vary in length
               after you get that information. You will also share an interesting fact about
               the local nature on the hikes when making a recommendation. At the end of your
               response, ask if there is anything else you can help with.
           """)
       ];
   

3. Create a conversational loop that accepts an input prompt from the user, sends the prompt to the model, and prints the response completion:

   // Loop to get user input and stream AI response
   while (true)
   {
       // Get user prompt and add to chat history
       Console.WriteLine("Your prompt:");
       string? userPrompt = Console.ReadLine();
       chatHistory.Add(new ChatMessage(ChatRole.User, userPrompt));
   
       // Stream the AI response and add to chat history
       Console.WriteLine("AI Response:");
       string response = "";
       await foreach (ChatResponseUpdate item in
           chatClient.GetStreamingResponseAsync(chatHistory))
       {
           Console.Write(item.Text);
           response += item.Text;
       }
       chatHistory.Add(new ChatMessage(ChatRole.Assistant, response));
       Console.WriteLine();
   }
   

4. Use the dotnet run command to run the app:

   dotnet run
   

   The app prints out the completion response from the AI model. Send additional follow up prompts and ask other questions to experiment with the AI chat functionality.

Next steps

• Quickstart - Chat with a local AI model
• Generate images using AI with .NET