Run async Task sychronously w/exception propagation

Question

What is the preferred way to run an async method synchronously?

This is what I currently do:

void RunSync() {
    var task = Task.Run(() => RunAsync());
    task.Wait();
}

async Task RunAsync() {
     throw Exception("test");
}

My problem with the above code is that task.Wait() throws an AggregateException rather than the actual exception thrown by RunAsync which is what I'd prefer.

Is there a way to propagate the actual exception from RunAsync without resorting to catching AggregateException and unwrapping?

score 3 · Accepted Answer · edited May 23 '17 at 12:32

3

Fast answer:

Change this:

var task = Task.Run(() => RunAsync());
task.Wait();

to this:

var task = RunAsync();
task.Wait();

You should not wrap async methods with Task.Run for running it. Read SO answers 'How to call async methods from sync context', e.g. How would I run an async Task<T> method synchronously?

edited May 23 '17 at 12:32

Community

1
1

answered Mar 04 '17 at 06:53

mukh1n

158
1
7

from your link- is all that dispatcher / message pumping stuff related to running in a windows / forms application? if i am running a console application should i be fine? – CoderBrien Mar 04 '17 at 07:05
There are some nuances in different environments (WinForms, Console App, IIS), but for your case it's not so important. – mukh1n Mar 04 '17 at 07:34
By the way, I strongly recommend to read articles by Stephen Cleary about asyncs (http://blog.stephencleary.com/2013/10/taskrun-etiquette-and-proper-usage.html). There is all you need to know about async keyword :) – mukh1n Mar 04 '17 at 07:37

score 1 · Answer 2 · answered Mar 04 '17 at 22:38

1

In order to unwrap the AggregateException, do this:

RunAsync().GetAwaiter().GetResult();

answered Mar 04 '17 at 22:38

Paulo Morgado

14,111
3
31
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Run async Task sychronously w/exception propagation

2 Answers2