Why can't I catch an exception from async code?

Question

Everywhere I read it says the following code should work, but it doesn\'t.

public async Task DoSomething(int x)
{
   try
   {
      // Asynchronous implemen         


        

Answer 1

Your code won't even compile cleanly at the moment, as the x++; statement is unreachable. Always pay attention to warnings.

However, after fixing that, it works fine:

using System;
using System.Threading.Tasks;

class Test
{
    static void Main(string[] args)
    {
        DoSomething(10).Wait();
    }

    public static async Task DoSomething(int x)
    {
        try
        {
            // Asynchronous implementation.
            await Task.Run(() => {
                throw new Exception("Bang!");
            });
        }
        catch (Exception ex)
        {
            Console.WriteLine("I caught an exception! {0}", ex.Message);
        }
    }
}

Output:

I caught an exception! Bang!

(Note that if you try the above code in a WinForms app, you'll have a deadlock because you'd be waiting on a task which needed to get back to the UI thread. We're okay in a console app as the task will resume on a threadpool thread.)

I suspect the problem is actually just a matter of debugging - the debugger may consider it unhandled, even though it is handled.