I have multiple tasks returning the same object type that I want to call using Task.WhenAll(new[]{t1,t2,t3}); and read the results.
Task.WhenAll(new[]{t1,t2,t3});
When I try using <
Looks like you are using the overload of WaitAll() that doesn't return a value. If you make the following changes, it should work.
WaitAll()
List[] all = await Task.WhenAll(new Task>[] { t, t2 }) .ConfigureAwait(false);