Exceptions cannot be caught

Context: Exceptions thrown from an async void method cannot be caught by the caller; they crash the process or cause the application to terminate.

using System;
using System.Threading.Tasks;

public class BadExample
{
    public static void Main()
    {
        try
        {
            BadAsyncVoid();
        }
        catch (Exception)
        {
            Console.WriteLine("This will never execute");
        }
        Console.ReadLine(); // process may crash before this
    }

    static async void BadAsyncVoid()
    {
        throw new InvalidOperationException("Crash");
    }
}

Solution

Return Task instead of void.

async Task GoodAsync()
{
    throw new InvalidOperationException("Will be caught");
}

Real-world usage example

Avoid in library code: Never expose async void in public API. Only use async void for UI event handlers where the framework handles exceptions.

Example: Async guidelines - avoid async void

Related sections

• 9.5 Avoiding async void
• 9.5.2 Hard to test