What is the difference between these two async code blocks?

Question

Task<int> task = new Task<int>(CountCharactersIntheFile);
task.Start();
int count=await task;

and

int count = await Task.Run(() => CountCharactersInTheFile());

which one should I use when I am writing asynchronous code as per readibility and velocity?

Answer 1

Let’s check the source. Task.Run basically calls Task.InternalStartNew with a bunch of default arguments. This is how that method works:

internal static Task InternalStartNew(
    Task creatingTask, Delegate action, object state, CancellationToken cancellationToken, TaskScheduler scheduler,
    TaskCreationOptions options, InternalTaskOptions internalOptions, ref StackCrawlMark stackMark)
{
    // Validate arguments.
    if (scheduler == null)
    {
        throw new ArgumentNullException("scheduler");
    }
    Contract.EndContractBlock();

    // Create and schedule the task. This throws an InvalidOperationException if already shut down.
    // Here we add the InternalTaskOptions.QueuedByRuntime to the internalOptions, so that TaskConstructorCore can skip the cancellation token registration
    Task t = new Task(action, state, creatingTask, cancellationToken, options, internalOptions | InternalTaskOptions.QueuedByRuntime, scheduler);
    t.PossiblyCaptureContext(ref stackMark);

    t.ScheduleAndStart(false);
    return t;
}

As you can see, it creates the task and then eventually starts it. It however does a bit more like scheduling it properly, and ensuring the context. So it’s probably a very good idea to use Task.Run whenever you can to avoid having to do all of this manually. But essentially they do “the same” thing, just in different depths.

Answer 2

Task<int> task = new Task<int>(CountCharactersIntheFile);
task.Start();
int count=await task;

and

int count = await Task.Run(() => CountCharactersInTheFile());

are same . There is no such Difference asper my understanding .just a minified/lambda formated of the first one