WPF按钮按下Windows 7的mulit-touch

I am developing a WPF kiosk like client that will be deployed on an HP TouchSmart Windows 7 machine with multi-touch enabled. My problem is that with Windows 7 multi-touch, the application does not recognize a finger 'tap' as a button press event, and therefore the button press Trigger to change color is never fired. I am developing a WPF kiosk like client that wi