Using Task vs Dispatcher for ui thread actions

Question

I know the technique about UI thread updating from another thread.

So I have these two methods/techniques, which one should I use?

Using Task:

var uiTask = Task.Factory.StartNew(() => {
  // change something on ui thread
  var action = theActionOnUiThread;
  if (action != null) {
    action();
  }
}, CancellationToken.None, TaskCreationOptions.None, TaskScheduler.FromCurrentSynchronizationContext());

Using Dispatcher:

Dispatcher.CurrentDispatcher.BeginInvoke(
  new Action(() => {
    // change something on ui thread
    var action = theActionOnUiThread;
    if (action != null) {
      action();
    }
  }));

If this is a WPF app then there is no "better", pick the one you like. — Hans Passant, Dec 15 '12 at 21:09
Do you want to wait for the operation to complete? How do you want to handle exceptions? — svick, Dec 15 '12 at 22:20
@svick i don't want to wait for this operation and handle the exceptions at the 'action' action. — punker76, Dec 15 '12 at 22:33

score 2 · Answer 1 · answered Dec 15 '12 at 21:12

From a technical point of view I doubt there is a 'best' here. however I'd go with the dispatcher approach:

it makes your intent more clear, namely that you want to get something done on the main ui thread
you don't need to boter with all the task factory options
Dispatcher makes it easier to hide everything behind an interface (1) allowing easy dependency injection and unit testing

(1) see here for example

score 1 · Answer 2 · answered Dec 17 '12 at 09:03

TaskScheduler.FromCurrentSynchronizationContext() does not guarantee returning you a TaskScheduler for the UI thread.

In fact it can sometimes return null, although these cases are rare and generally involve spinning up your own dispatcher in a native app (for example the WIX bootstrapper).

So I'd say it's safer to use the dispatcher version.

Using Task vs Dispatcher for ui thread actions

2 Answers2