[Supported] When focus is not going to the containing ElementHost control, the Enter and Leave events are raised as usual when focus changes in a single WindowsFormsHost control. [Not supported] Enter and Leave events are not raised when the following focus changes occur: From inside to outside a WindowsFormsHost control. From outside to inside a WindowsFormsHost control. Outside a WindowsFormsHost control. From a Windows Forms control hosted in a WindowsFormsHost control to an ElementHost control hosted inside the same WindowsFormsHost. [Behavior] 
Enter and Leave Events