Why doesn't this exception get thrown?

Question

I use a set of tasks at times, and in order to make sure they are all awaited I use this approach:

public async Task ReleaseAsync(params Task[] TaskArray)
{
         


        

Answer 1

From the comment:

these [tasks] were tied to managed resources and I wanted to release them when they became available instead of waiting for all of them to complete and then releasing.

Using a helper async void method may give you the desired behavior for both removing the finished tasks from the list and immediately throwing unobserved exceptions:

public static class TaskExt
{
    public static async void Observe(Task task)
    {
        await task;
    }

    public static async Task WithObservation(Task task)
    {
        try
        {
            return await task;
        }
        catch (Exception ex)
        {
            // Handle ex
            // ...

            // Or, observe and re-throw
            task.Observe(); // do this if you want to throw immediately

            throw;
        }
    }
}

Then your code might look like this (untested):

async void Main()
{
    Task[] TaskArray = new Task[] { run().WithObservation() };
    var tasks = new HashSet(TaskArray);
    while (tasks.Any()) tasks.Remove(await Task.WhenAny(tasks));
}

.Observe() will re-throw the task's exception immediately "out-of-band", using SynchronizationContext.Post if the calling thread has a synchronization context, or using ThreadPool.QueueUserWorkItem otherwise. You can handle such "out-of-band" exceptions with AppDomain.CurrentDomain.UnhandledException).

I described this in more details here:

TAP global exception handler