如何分派到主线程？

Question

I would like to execute some code from a non-main thread inside the main thread (UI thread) in.Net 6 with C#.

I've tried to use this code:

await Windows.UI.Core.CoreWindow.GetForCurrentThread().Dispatcher.RunAsync(
    Windows.UI.Core.CoreDispatcherPriority.Normal,
    () => { }
);

This doesn't work, since Windows.UI.Core.CoreWindow.GetForCurrentThread() returns null .

My second try was:

await Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
    Windows.UI.Core.CoreDispatcherPriority.Normal,
    () => { }
);

This fails, because Windows.ApplicationModel.Core.CoreApplication.MainView throws a System.InvalidOperationException .

Another way should be:

await System.Windows.Threading.Dispatcher.RunAsync(
    Windows.UI.Core.CoreDispatcherPriority.Normal,
    () => { }
);

But the System.Windows.Threading namespace is not available for me, since I'm using.Net 6 and it's not longer supported in it.

Any idea, how I can execute some code from a non-main thread inside the main-thread (UI thread)?

Answer 1

I would like to execute some code from a non-main thread inside the main thread (UI thread) in.Net 6 with C#.

I strongly recommend that you don't . It's far cleaner to have your async methods use something like IProgress<T> to indirectly update the UI as necessary. If you structure your code so that the main thread calls the background threads instead of the background threads manipulating the UI through the UI thread, then you'll end up with a much cleaner design where your logic is less tied to your UI controls.

That said, if you really want to, then the solution is to capture the dispatcher on the UI thread before the background work begins, and have the background work use that dispatcher (not the "current dispatcher") when posting work to the UI thread.

Answer 2

SynchronizationContext is a good solution to switch to the main thread. But it's not implemented for all.Net app types.

For example, for a console app, there is no solution implemented.

But for Windows Forms, WindowsFormsSynchronizationContext works fine.

private SynchronizationContext _synchronizationContext;

Initialization inside, called inside the main thread:

_synchronizationContext = new WindowsFormsSynchronizationContext();

After this, you can call from a different thread:

SynchronizationContext.SetSynchronizationContext(_synchronizationContext);

... here we are in a separate thread

_synchronizationContext.Post(
    (state) => {
        ... this will be executed in the main thread
    },
    null);

Answer 3

            await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync
            (CoreDispatcherPriority.Normal, () =>
            {
            do something on UI thread
             });