preventing page from being redirected

Question

I was wondering if anyone knew a way to prevent a page from being redirected? I would like to capture an event when the page is leaving, then run some code behind. If the code behind meets certain criteria, then allow the redirect, otherwise cancel it. I know some of this can be accomplished with Javacript but the problem I have is actually stopping the redirect. Here's what I have:

JavaScript:

<script type="text/javascript">
   window.onbeforeunload = confirmExit;

   function clickButton(getId) {
            var getBtn = document.getElementById(getId)
            getBtn.click()
        } 

   function confirmExit(e) {
       var btnId = document.getElementById("<%=btnConfirmExit.ClientId %>").id
       clickButton(btnId)
    }
 </script>  

Code behind:

Protected Sub btnConfirmExit_click(ByVal sender As Object, ByVal e As EventArgs) Handles btnConfirmExit.Click
    'if something, cancel request

    'else
     ' let it go
end Sub

If tried using:

Page.Response.End()

But this does nothing. Anyone have any ideas?

Thanks

Answer 1

If your are using classic postBacks, the browser has already begun requesting and listening for a new page, and there is no 'nevermind' HTTP response. Even if you got this to work on some browsers in some circumstances, it would be inconsistent and unreliable.

I think you want to look into using an AJAX request if you have to do this validation/processing server side.

I'm not a fan of them, but worst case, down and dirty and without changing much code, you can use an Update Panel. Read about it here:

newer info: http://msdn.microsoft.com/en-us/library/bb398864(v=vs.100).aspx

older link, but nice overview: http://www.asp.net/ajax/documentation/live/overview/updatepaneloverview.aspx