C# Feature - async Main

async Main

async Main allows a console application’s entry point to return Task or Task<int>, so startup code can await asynchronous operations directly instead of blocking on them.

Introduced In

This feature was introduced in C# 7.1 (2017).

Why This Feature Exists

Before C# 7.1, async startup logic usually meant forcing asynchronous code into synchronous flow with .Result, .Wait(), or .GetAwaiter().GetResult(). That approach is harder to read and can hide failure behavior.

With async Main, the entry point follows the same async style as the rest of the codebase.

Supported Signatures

static async Task Main()
static async Task Main(string[] args)
static async Task<int> Main()
static async Task<int> Main(string[] args)

When To Use It

Use it in console applications that call HTTP APIs, databases, files, queues, or any other async dependency during startup.
Use Task<int> when the process should return an exit code.
Prefer it over blocking on async work manually.

Before

static int Main()
{
  RunAsync().GetAwaiter().GetResult();
  return 0;
}

After

static async Task Main()
{
  await RunAsync();
}

Practical Example

using System.Net.Http;

static async Task<int> Main(string[] args)
{
  using var client = new HttpClient();

  try
  {
    string health = await client.GetStringAsync("https://example.com/health");
    Console.WriteLine($"Service health: {health}");
    return 0;
  }
  catch (HttpRequestException ex)
  {
    Console.Error.WriteLine($"Startup check failed: {ex.Message}");
    return 1;
  }
}

Common Pitfalls

Do not mix async Main with .Result or .Wait() unless there is a very specific reason.
async void is not a valid entry point signature.
Startup code can still fail fast, so exception handling should be deliberate rather than implicit.

Version Notes

C# 7.1 introduced asynchronous entry points.
C# 9 top-level statements can also produce an async entry point implicitly when await is used.