Why doesn't await on Task.WhenAll throw an AggregateException?

Question

In this code:

private async void button1_Click(object sender, EventArgs e) {
    try {
        await Task.WhenAll(DoLongThingAsyncEx1(), DoLongThingAsyncEx2(         


        

Answer 1

In your code, the first exception is returned by design as explained at http://blogs.msdn.com/b/pfxteam/archive/2011/09/28/task-exception-handling-in-net-4-5.aspx

As for your question, you will get the AggreateException if you write code like this:

try {
    var result = Task.WhenAll(DoLongThingAsyncEx1(), DoLongThingAsyncEx2()).Result; 
}
catch (Exception ex) {
    // Expect AggregateException here
}