How do I programmatically change focus?

You can programmatically change focus to another user interface element using the MoveFocus() method.

First, you need to determine which UI element has focus. For example:

IInputElement focusedElement = FocusManager.GetFocusedElement(thisWindow);

Next, you cast the element to UIElement and call its MoveFocus() method:

UIElement uiElement = focusedElement as UIElement;

uiElement.MoveFocus(new TraversalRequest(FocusNavigationDirection.Next));

The FocusNavigationDirection enumeration includes options such as Down, First, Last, Left, Next, Previous, Right, and Up