wpf to handle touch keyboard in windows 8 desk mode

I have tried to show touch keyboard using IInputPanelConfiguration interface.

http://msdn.microsoft.com/ja-jp/library/windows/desktop/jj126267(v=vs.85).aspx 

It worked on MFC project. but it not work well on my wpf project.

I added a WebBrowser and a TextBox to my wpf project. The touch keyboard is shown when the searchbox of the webpage shown in the my WebBrowser, but the touch keyboard doesn't show when touch the TextBox.

best regards.