WPF - Why isn't Keyboard.Focus() working?

Question

have a TextBox item (MyTextBox) on a TabItem control. I have code that looks as follows:

MyTextBox.Focus();
Keyboard.Focus(MyTextBox);

When I run this code through the debugger I see the following after the lines are executed:

MyTextBox.IsFocused = true
MyTextBox.IsKeyboardFocused = false

Can anyone tell me why the textbox isn't receiving keyboard focus? It's just a standard TextBox control that is enabled.

Answer 1

When you try to set Focus to an element besides the things enumerated above by our coleague, you must also know that WPF does not allow cross threaded operations.

In some cases this exception is not raised like in the Focus method call case. What I've done to fix this issue is to call all the code that involves Keyboards focus in an action.

This action is ran inside the control dispatcher to make sure that my code is not being executed from another thread than the UI thread (e.g. timer event or an event raised from another thread):

[UIElement].Dispatcher.BeginInvoke(
      new Action(
         delegate{
             /// put your Focus code here
         }
      )
);