C# AggregateException, in what scenario would I have aggregated exceptions?

Question

I am probably missing a very obvious fact, but I have a hard time understanding the need for AggregatedExceptions.

I know since async/await we don't have to bother with AggregatedExceptions anymore (or at least are confronted with them less frequently). I can relate to that, because I simply start a task and at some time I choose to synchronize the 'calling thread' with the 'task which runs in parallel'

var sometTask = DoSomethingInParallelAsync().ConfigureAwait(false);
...
...
await someTask;

In this scenario, an exception that occurred in DoSomethingInParallelAsync() will be presented to me when I await that call.

Why is that so different without using await , but Wait on the Task explicitly?

var someTask = DoSomethingInParallelAsync();
...
...
someTask.Wait();

An exception thrown in this example, will always wrap the thrown Exception in an AggregateException . I still don't understand why.

What can't I do when using async/await which takes away the need for AggregateException s?

Answer 1

Causing and handling the error

Task task1 = Task.Factory.StartNew(() => { throw new ArgumentException(); } );
Task task2 = Task.Factory.StartNew(() => { throw new UnauthorizedAccessException(); } );

try
{
    Task.WaitAll(task1, task2);
}
catch (AggregateException ae)
{
}

and also see that links

here is an example: link2