> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/microsoft/autogen/llms.txt
> Use this file to discover all available pages before exploring further.

# Quick Start

> Build your first AutoGen application in C#

## Prerequisites

Before you begin, make sure you have:

* .NET 6.0 or later installed
* An OpenAI API key
* Visual Studio, VS Code, or your preferred C# IDE

## Installation

Install the AutoGen package, which includes all core features:

```bash theme={null}
dotnet add package AutoGen
```

For more granular control, see the [Installation Guide](/dotnet/installation).

## Your First Agent Conversation

Let's create a simple conversation between a user and an AI assistant.

<Steps>
  <Step title="Create a new console application">
    ```bash theme={null}
    dotnet new console -n AutoGenQuickStart
    cd AutoGenQuickStart
    dotnet add package AutoGen
    ```
  </Step>

  <Step title="Set up your OpenAI API key">
    Set your OpenAI API key as an environment variable:

    <CodeGroup>
      ```bash Windows (PowerShell) theme={null}
      $env:OPENAI_API_KEY="your-api-key-here"
      ```

      ```bash macOS/Linux theme={null}
      export OPENAI_API_KEY="your-api-key-here"
      ```
    </CodeGroup>
  </Step>

  <Step title="Create the application">
    Replace the contents of `Program.cs` with:

    ```csharp Program.cs theme={null}
    using AutoGen;
    using AutoGen.OpenAI;

    var openAIKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY") 
        ?? throw new Exception("Please set OPENAI_API_KEY environment variable.");

    var gpt35Config = new OpenAIConfig(openAIKey, "gpt-3.5-turbo");

    // Create an assistant agent
    var assistantAgent = new AssistantAgent(
        name: "assistant",
        systemMessage: "You are a helpful assistant that can answer questions and help with tasks.",
        llmConfig: new ConversableAgentConfig
        {
            Temperature = 0,
            ConfigList = [gpt35Config],
        })
        .RegisterPrintMessage(); // Print messages to console

    // Create a user proxy agent
    var userProxyAgent = new UserProxyAgent(
        name: "user",
        humanInputMode: HumanInputMode.ALWAYS) // Always ask for user input
        .RegisterPrintMessage();

    // Start the conversation
    await userProxyAgent.InitiateChatAsync(
        receiver: assistantAgent,
        message: "Hey assistant, please help me write a C# function to calculate factorial.",
        maxRound: 10);
    ```
  </Step>

  <Step title="Run the application">
    ```bash theme={null}
    dotnet run
    ```

    The application will start a conversation where you can interact with the AI assistant. Type your messages and press Enter. The conversation continues until you reach the maximum rounds or terminate it.
  </Step>
</Steps>

## Understanding the Code

### AssistantAgent

The `AssistantAgent` is an AI-powered agent that uses a language model to generate responses:

```csharp theme={null}
var assistantAgent = new AssistantAgent(
    name: "assistant",
    systemMessage: "You are a helpful assistant.",
    llmConfig: new ConversableAgentConfig
    {
        Temperature = 0,
        ConfigList = [gpt35Config],
    });
```

* **name**: Unique identifier for the agent
* **systemMessage**: Instructions that define the agent's behavior
* **llmConfig**: Configuration including model settings and API keys
* **Temperature**: Controls randomness (0 = deterministic, 1 = creative)

### UserProxyAgent

The `UserProxyAgent` represents a human user in the conversation:

```csharp theme={null}
var userProxyAgent = new UserProxyAgent(
    name: "user",
    humanInputMode: HumanInputMode.ALWAYS);
```

* **HumanInputMode.ALWAYS**: Prompts for user input before each message
* **HumanInputMode.NEVER**: Fully autonomous (uses default replies)
* **HumanInputMode.TERMINATE**: Only prompts when termination is suggested

### Message Printing

The `RegisterPrintMessage()` middleware nicely formats and prints messages to the console:

```csharp theme={null}
.RegisterPrintMessage()
```

### InitiateChatAsync

Starts the conversation between agents:

```csharp theme={null}
await userProxyAgent.InitiateChatAsync(
    receiver: assistantAgent,
    message: "Initial message",
    maxRound: 10);
```

## Autonomous Mode Example

For a fully autonomous conversation without human input:

```csharp theme={null}
using AutoGen;
using AutoGen.OpenAI;

var openAIKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY");
var gpt35Config = new OpenAIConfig(openAIKey, "gpt-3.5-turbo");

var assistant = new AssistantAgent(
    name: "assistant",
    systemMessage: "You are a helpful coding assistant.",
    llmConfig: new ConversableAgentConfig
    {
        Temperature = 0,
        ConfigList = [gpt35Config],
    })
    .RegisterPrintMessage();

var user = new UserProxyAgent(
    name: "user",
    humanInputMode: HumanInputMode.NEVER,
    defaultReply: "Thank you!")
    .RegisterPrintMessage();

await user.InitiateChatAsync(
    receiver: assistant,
    message: "Write a C# function to check if a number is prime.",
    maxRound: 3);
```

## Next Steps

<CardGroup cols={2}>
  <Card title="Agents" icon="robot" href="/dotnet/agents">
    Learn more about agent types and configurations
  </Card>

  <Card title="Function Calling" icon="function" href="/dotnet/function-calling">
    Add custom functions to your agents
  </Card>

  <Card title="Group Chat" icon="users" href="/dotnet/group-chat">
    Create multi-agent conversations
  </Card>

  <Card title="Code Execution" icon="terminal" href="/dotnet/code-execution">
    Execute code snippets dynamically
  </Card>
</CardGroup>

## Troubleshooting

<AccordionGroup>
  <Accordion title="API Key Not Found">
    Make sure you've set the `OPENAI_API_KEY` environment variable correctly. In Windows, you may need to restart your terminal or IDE after setting it.
  </Accordion>

  <Accordion title="Package Not Found">
    Ensure you're using .NET 6.0 or later and that you've restored packages:

    ```bash theme={null}
    dotnet restore
    ```
  </Accordion>

  <Accordion title="Connection Errors">
    Check your internet connection and verify that your OpenAI API key is valid and has sufficient credits.
  </Accordion>
</AccordionGroup>