Parent widnow blocking when pop up opened

Hello experts,
I am using MVC4, in my requirement model popup having some functionality, I need to block the parent window until closing or saving the popup window , I am able to block the disable scroll bar and mouse wheel when accessing the popup, but if I am trying to drag the popup, its diappearing and the application is freezing , please suggest me in this issue if any body having any solution.

Thanks in Advance.