.NET Framework 4.6 and 4.5
public static void ClearFocus()
If focus is within a Win32 window, WPF calls the ClearFocus method on restoration of focus when a menu is closed.
When leaving menu mode, Win32 focus is returned to the hosted child HWND, and no element has WPF focus.
Supported in: 4.6, 4.5, 4
.NET Framework Client Profile
Supported in: 4