Correct way to get the CoreDispatcher in a Windows Store app

Question

I'm building a Windows Store app, and I have some code that needs to be posted to the UI thread.

For that, i'd like to retrieve the CoreDispatcher and use it to post the code.

It seems that there are a few ways to do so:

// First way
Windows.ApplicationModel.Core.CoreApplication.GetCurrentView().CoreWindow.Dispatcher;

// Second way
Window.Current.Dispatcher;

I wonder which one is correct? or if both are equivalent?

Answer 1

This is the preferred way:

Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.Normal,
() =>
{
    // Your UI update code goes here!
});

The advantage this has is that it gets the main CoreApplicationView and so is always available. More details here.

There are two alternatives which you could use.

First alternative

Windows.ApplicationModel.Core.CoreApplication.GetCurrentView().CoreWindow.Dispatcher

This gets the active view for the app, but this will give you null, if no views has been activated. More details here.

Second alternative

Window.Current.Dispatcher

This solution will not work when it's called from another thread as it returns null instead of the UI Dispatcher. More details here.

Answer 2

For anyone using C++/CX

Windows::ApplicationModel::Core::CoreApplication::MainView->CoreWindow->Dispatcher->RunAsync(
    CoreDispatcherPriority::Normal,
    ref new Windows::UI::Core::DispatchedHandler([this]()
{
    // do stuff
}));

Answer 3

await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
            CoreDispatcherPriority.Normal,
            () => { // your code should be here});

Answer 4

Actually, I would propose something in the line of this:

return (Window.Current == null) ? 
    CoreApplication.MainView.CoreWindow.Dispatcher : 
    CoreApplication.GetCurrentView().CoreWindow.Dispatcher

That way, should you have openend another View/Window, you won't get the Dispatchers confused...

This little gem checks whether there is even a Window. If none, use the MainView's Dispatcher. If there is a view, use that one's Dispatcher.