Calling an async method without await

Question

I'm currently calling an async method and don't want to await it. I don't need the result for the async method and don't want to block during IO. However, if there is an error thrown in the async method I would like to catch it. So far I have:

public static void main () {
    MyAsyncMethod().
    ContinueWith(t => Console.WriteLine(t.Exception),
           TaskContinuationOptions.OnlyOnFaulted);
    //dostuff without waiting for result
}

This is not catching the exception thrown in MyAyncMethod from Main. Is there something I'm doing wrong?

I assumed that Continuewith would "catch" the exception. Atleast, that's what I read but currently my code crashes — user3750474
– user3750474, Commented Oct 26, 2015 at 22:54

Scott Chamberlain · Accepted Answer · 2015-10-26 21:14:17Z

2

async-await and ContinueWith can work but it is full of headaches. It is much easier just refactor out your error handling in to a method and put it in there, then you can just call that new method from your main method.

public static void main () {
    var task = DoMyAsyncMethod();

   //dostuff without waiting for result

    //Do a wait at the end to prevent the program from closing before the background work completes. 
    task.Wait();

}

private static async Task DoMyAsyncMethod()
{
    try
    {
        await MyAsyncMethod();
    }
    catch (Exception e)
    {
        Console.WriteLine(e);
    }
}

I suspect the real problem you are dealing with is that missing Wait() and your program is closing itself before your background work is done processing.

answered Oct 26, 2015 at 21:14

Scott Chamberlain

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2 Comments

user3750474 Over a year ago

Our program will always be running on a server so we will never wait. Won't this still block in DoMyAsyncMethod ?

Scott Chamberlain Over a year ago

No, when you hit the await the function DoMyAsyncMethod will retun a Task object, it will not block. It is up to you want you want to do with that Task, wait on it, throw it away, it does not matter. A await really is just a easier way to do work with a ContinueWith, it lets you write async code the same way you write sync code (for example, using a try/catch instead of a ContinueWith(SomeMethod, TaskContinuationOptions.OnlyOnFaulted)).

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