wpf app ran in win8 pad,screen rotate problem

Hi,

I have a wpf app,which run in win8 pad,now i want to how resove the problem:when the app  windowstyle=none ,windowstate= maximized, and use win32 API handle the taskbar visible i roate the screen form landscape to protrait mode, found the app's rendersize error :actualHeight != Height

Ps:before the app ran,the screen in landscape mode.

Is there other method to solve the problem