Static Field Initialization

Question

private readonly CoreDispatcher dispatcher;

I am initializing above field in constructor to CoreWindow.GetForCurrentThread().Dispatcher; Then I wrapped a function around it:

public async Task OnUiThread(Action action)
{
    await dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => action());
}

and using this function to transfer calls to UIThread whneva required.It works fine.

Since I was doing this on every page of my application I decided to rathar maker a static class say

public static class ThreadManager
{
    private static readonly CoreDispatcher dispatcher;

    static ThreadManager()
    {
        dispatcher = CoreWindow.GetForCurrentThread().Dispatcher;
    }

    public static async Task OnUiThread(Action action)
    {
        await dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => action());
    }
}

but now when I try to use this on my pages to transfer calls to UI thread, I get object null exception and dispatcher is shown null everywhere on other pages whereva I make the call to this static class. Why?

Answer 1

Well, you're initializing the CoreDispatcher based on whichever thread happens to initialize the class. Given that you really want it to be done for a specific dispatcher, this feels like it's a bad idea to me.

Given that you're using this from a page, can't you use the dispatcher for that page instead? I don't see why you need a dispatcher variable at all... you might consider writing an extension method for OnUiThread instead.

Also, you don't really need to use async/await here - or a lambda expression. You can just use:

public static Task OnUiThread(this CoreDispatcher dispatcher, Action action)
{
    return dispatcher.RunAsync(CoreDispatcherPriority.Normal,
                               new DispatchedHandler(action))
                     .AsTask();
}