I want await to throw AggregateException, not just the first Exception

Question

When awaiting a faulted task (one that has an exception set), await will rethrow the stored exception. If the stored exception is an AggregateException

Answer 1

I don't want to give up the practice to only catch the exceptions I expect. This leads me to the following extension method:

public static async Task NoSwallow(this Task task) where TException : Exception {
    try {
        await task;
    } catch (TException) {
        var unexpectedEx = task.Exception
                               .Flatten()
                               .InnerExceptions
                               .FirstOrDefault(ex => !(ex is TException));
        if (unexpectedEx != null) {
            throw new NotImplementedException(null, unexpectedEx);
        } else {
            throw task.Exception;
        }
    }
}

The consuming code could go like this:

try {
    await Task.WhenAll(tasks).NoSwallow();
catch (AggregateException ex) {
    HandleExceptions(ex);
}

A bone-headed exception will have the same effect as in synchronous world, even in case it is thrown concurrently with a MyException by chance. The wrapping with NotImplementedException helps to not loose the original stack trace.