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Detect Close Browser in ASP.NET

Thread ID:





108924 May 21,2013 02:55 PM UTC May 28,2013 12:43 PM UTC ASP.NET Web Forms (Classic) 1
Tags: Tools
Hayssam Hassan
Asked On May 21, 2013 02:55 PM UTC

I have a ASP.NET web app with a MasterPage and contents page, from the MasterPage i define a menuItems like "Home", "New" and "Logout". I click  the "New" MenuItem to open a new aspx Page. if I want to close the new page browser tab, I want to show a popup or a dialog that alert the user that he/ she is closing the browser tab. I used the following code in the new aspx page:

 <script type="text/javascript">
        var warnMessage = "Are sure you want to close Application?";
        window.onbeforeunload = function () { return warnMessage };
        $(document).ready(function () {
            $('a').click(function () { window.onbeforeunload = null; });
            $('form').submit(function () { window.onbeforeunload = null; });
the problem is that if i press also other buttons or menuItems than the browse closeTab the method works. i would like to know how can i avoid it. i think i need to detect the Syncfusion MenuItem event but i dont know how.

Sunil Prabakar C [Syncfusion]
Replied On May 28, 2013 12:43 PM UTC

Hi Hayssam Hassan,


Thanks for using Syncfusion products.


To avoid showing alert on clicking menuitem or button we have maintained a flag variable in "Menu" control’s cliendSideevent "ClientSideOnItemSelect"

and "Button" control’s cliendsideevent "OnClientClick" .Therefore, alert will be shown only if the flag is false.


Please refer the following code snippet





<script type="text/javascript">

        var event = 0;       //falg variable

        function buttonClick() {

            event = 1;                //set falg true


        function menuClick() {

            event = 1;                //set flag true


        var warnMessage = "Are sure you want to close Application?";

        window.onbeforeunload = function () {

            if (event === 0) { 

                return warnMessage




        $(document).ready(function () {

            $('a').click(function () { window.onbeforeunload = null; });

            $('form').submit(function () { window.onbeforeunload = null; });







  <syncfusion:Menu ID="Menu" runat="server" ClientSideOnItemSelect="menuClick()">

  <asp:Button ID="btn" runat="server" Text="Button Sample" OnClientClick="return buttonClick()" />




We have also prepared a simple sample to showcase this behavior and the sample can be downloaded from the link given below



Kindly try the attached sample  and let us know if this helps.


Thanks & Regards

Sunil Prabakar C



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