Question

In Winforms, all controls have an InvokeRequired property, that returns true if I have to call .[Begin]Invoke on the control in order to modify it.

In WPF, there is an apparently similar construct in DispatcherObject.CheckAccess() and Dispatcher.CheckAccess(), but I am frightened by the EditorBrowsable(EditorBrowsableState.Never) attribute. When I disable editor browsing like this, I use it to means “You should not be doing this. No, really. If this is required solve your immediate problem, you have mis-designed your solution to your overarching problem.” On the other hand, the only alternative I’ve found (and, in fact, my original solution) is Thread.CurrentThread.ManagedThreadId == 1. (It’s horrible. And it doesn’t work in the generic case. I know. It does work for my limited uses, though.)

The MSDN documentation is silent on the presence of and reasoning behind the EditorBrowsable attribute. Does it indeed mean “do not use this”, as it would if I had typed it, or does it have some other less prohibitive meaning?

Answer 1

In WPF, you can call Dispatcher.Invoke regardless of your current thread, and it’ll handle the call accordingly – if you’re already on the right thread, it’ll just invoke your code, and it uses CheckAccess to handle this behaviour.

For a BeginInvoke the thread you’re currently on is irrelevant: BeginInvoke is always asyncronous, and the order of execution is dependant on the priority of the item you add to the dispatcher’s queue.

If you weren’t supposed to use the method at all, it wouldn’t be public: the intent of that attribute is only to hide the member from mechanisms such as Intellisense and other editor-browsers. You don’t typically need to use Dispatcher.CheckAccess() yourself, which is probably why it’s marked as non-browsable, but the wisdom of this is something we can only guess at (unless Eric Lippert is watching 😉

In summary: just call Dispatcher.Invoke and don’t worry about CheckAccess.