My button on click is not working.

I have a registration page in that page I have a text box for mobile number and a button in my designing page but when I click on the submit button its not fire in the coding page where the method `button_click` define. when I use `UseSubmitBehaviour="false"` in my button its working but its not holding the value of text box where I define the mobile number and its shows that mobile number can't be empty.