Task sequencing and re-entracy

Question

I\'ve got the following scenario, which I think might be quite common:

1. There is a task (a UI command handler) which can complete either synchronously or asy

Answer 1

Here is a solution that is worse on every aspect compared to the accepted answer, except from being thread-safe (which is not a requirement of the question). Disadvantages:

1. All lambdas are executed asynchronously (there is no fast path).
2. The executeOnCurrentContext configuration effects all lambdas (it's not a per-lambda configuration).

This solution uses as processing engine an ActionBlock from the TPL Dataflow library.

public class AsyncOp
{
    private readonly ActionBlock>> _actionBlock;

    public AsyncOp(bool executeOnCurrentContext = false)
    {
        var options = new ExecutionDataflowBlockOptions();
        if (executeOnCurrentContext)
            options.TaskScheduler = TaskScheduler.FromCurrentSynchronizationContext();

        _actionBlock = new ActionBlock>>(async taskTask =>
        {
            try
            {
                taskTask.RunSynchronously();
                await await taskTask;
            }
            catch { } // Ignore exceptions
        }, options);
    }

    public Task RunAsync(Func> taskFactory)
    {
        var taskTask = new Task>(taskFactory);
        if (!_actionBlock.Post(taskTask))
            throw new InvalidOperationException("Not accepted"); // Should never happen
        return taskTask.Unwrap();
    }
}