`async void` Anti-Pattern & Global Crash Traps

1Concept

`async void` methods cannot be awaited and unhandled exceptions cannot be caught by surrounding `try-catch` blocks, causing the entire process to crash immediately.

2Architecture Diagram

async Task Method(): ──> Caller can `await` and catch exceptions inside `try-catch`
async void Method(): ──> Exceptions bypass catch blocks and crash CLR process!

3Code Example

using System;
using System.Threading.Tasks;

public class AsyncVoidTrapDemo
{
    // Good: Returns Task
    public static async Task SafeAsyncMethod()
    {
        await Task.Delay(5);
        Console.WriteLine("Safe async task completed.");
    }

    public static async Task Main()
    {
        await SafeAsyncMethod();
        Console.WriteLine("Only top-level UI event handlers (e.g. Button_Click) should use async void.");
    }
}

4Expected Output

Safe async task completed.
Only top-level UI event handlers (e.g. Button_Click) should use async void.

5Key Takeaways

• ✓Never use `async void` except in top-level UI event handlers.
• ✓Always return `Task` or `ValueTask` for async methods.
• ✓Async void exceptions trigger `AppDomain.UnhandledException` directly.