Catch exception of a async method

Question

Hello I want to catch a Exception of a async method but it did not work look a this example :

        public void TryToCatchException()
        {
            try
            {
                _ =LongRunningMethod();
            }
            catch (MyException)
            {
                Console.WriteLine("catched");
            }
        }


        public static async Task LongRunningMethod()
        {
            await Task.Run(() =>
            {
                try
                {
                    Task.Delay(1000); //simulation of work
                    throw new ArgumentException(); // this is a example
                }
                catch (ArgumentException)
                {
                    throw new MyException;
                }

            });
        }

if I launch the debugger will say that the exception "MyException" is NOT catched... can someone help me ?

@JHBonarius because I use a API Method that block the current thread for 10 to 15 seconds and I don't want that. — Tiklyt
– Tiklyt, Commented Apr 10, 2021 at 15:33
As you don't await LongRunningMethod, TryToCatchException will return (almost) immediately and cannot catch any exceptions. — Klaus Gütter
– Klaus Gütter, Commented Apr 10, 2021 at 15:58

Stephen Cleary · Accepted Answer · 2021-04-10 15:58:20Z

3

When you discard tasks, those exceptions are not observed:

_ =LongRunningMethod();

If you want to catch exceptions from LongRunningMethod, then you need to await the task returned from that method:

await LongRunningMethod();

answered Apr 10, 2021 at 15:58

Stephen Cleary

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2 Comments

Tiklyt Over a year ago

Thanks you for your comment, but my debugger still say that the exception is "Exception User-Unhandled". ^^ That is normal ?

Stephen Cleary Over a year ago

Yes, when you run it in the debugger.

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