AJAX :: ModalPopUp Not Rendering Properly

Whenever you have something like this:

MsgBox("Message before page load")
Response.Redirect("xyz.aspx")

The message box pops up and when you click ok in messagebox then you get redirected to xyz page. I am using Ajaxmodalpopupexntender instead of Message box which loads a UserControl into it. After the popup I have response.redirect. Now, my modalpop doesn't render on to the screen before redirect, waiting for Ok button to be clicked and then get redirected. It directly gets redirected to the xyz page without loading the popup.