Equivalent to InvokeRequired in WPF

Question

Is there an equivalent to Form.InvokeRequired in WPF, e.g. Dispatcher.InvokeRequired?

Answer 1

If you're building a Windows Store app, the above example won't work. Here's an example that does work. Modify as needed, of course :)

/// <summary>
/// Updates the UI after the albums have been retrieved. This prevents the annoying delay when receiving the albums list.
/// </summary>
/// <param name="albums"></param>
public void UpdateUiAfterAlbumsRetrieved(System.Collections.ObjectModel.ObservableCollection<PhotoAlbum> albums)
{
    if (!Dispatcher.HasThreadAccess)
    {
        Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
        {
            ddlAlbums.DataContext = albums;
            ddlAlbums.IsEnabled = true;
            tbxProgress.Text = String.Empty;
            ProgressBar.IsIndeterminate = false;
            ProgressBar.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
        });
    }
    else
    {
        ddlAlbums.DataContext = albums;
        ddlAlbums.IsEnabled = true;
        tbxProgress.Text = String.Empty;
        ProgressBar.IsIndeterminate = false;
    }
}

Answer 2

The equivalent is Dispatcher.CheckAccess.

Answer 3

This is slightly odd as it doesn't appear in intellisense, but you can use:

var dispatcher = myDispatcherObject.Dispatcher;
if (dispatcher.CheckAccess()) { /* ... */ }

As all UI components inherit from DispatcherObject this should solve your specific problem, but it is not specific to the UI thread - it can be used for any dispatcher.

Answer 4

A possible solution that came to mind is:

if ( Dispatcher.Thread.Equals( Thread.CurrentThread ) )
{
    Action( );
}
else
{
    Dispatcher.Invoke( Action );
}