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Alert Session Time out in ASP.NET

, 27 Jul 2011
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This article looks at ways to warn users about the session timeout.

Introduction

One of the requirements in my project was to warn users about the session expiry. Though it looks like a simple requirement for the end users, it is not the case for developers and designers. We need to deal with lot of scenarios in the real time application. What is the best way to achieve the objective? Some of the challenges would be like:

  1. Session is a sliding expiry value. It gets extended every time there is a post back.
  2. There are multiple ways that you can handle this scenario and each of them has its own technical challenges.

Approaches

The following section will try to cover few of the approaches to handle session expiry.

1. Provide a Simple Alert

In this approach, the user will be provided with a simple warning message, based on a pre-defined time interval.

<script language="javascript" type="text/javascript">
       var sessionTimeoutWarning = 
	"<%= System.Configuration.ConfigurationSettings.AppSettings
	["SessionWarning"].ToString()%>";
        var sessionTimeout = "<%= Session.Timeout %>";

        var sTimeout = parseInt(sessionTimeoutWarning) * 60 * 1000;
        setTimeout('SessionWarning()', sTimeout);

        function SessionWarning() {
var message = "Your session will expire in another " + 
	(parseInt(sessionTimeout) - parseInt(sessionTimeoutWarning)) + 
	" mins! Please Save the data before the session expires";
alert(message);
        }
</script>
  • sessionTimeoutWarning: is a predefined value in the application configuration. Say 18 minutes.
  • sessionTimeout: holds the session timeout interval. Say 20 minutes. In case the user does not do any post back on the page for about 18 minutes, he will be warned about the session expiry.

2. Provide a Simple Alert and Then Redirect the User to Home Page or Login Page

  <script language="javascript" type="text/javascript">
        var sessionTimeoutWarning = 
	"<%= System.Configuration.ConfigurationSettings.AppSettings
	["SessionWarning"].ToString()%>";
        var sessionTimeout = "<%= Session.Timeout %>";
        var timeOnPageLoad = new Date();
 
        //For warning
        setTimeout('SessionWarning()', parseInt(sessionTimeoutWarning) * 60 * 1000);
        //To redirect to the welcome page
        setTimeout('RedirectToWelcomePage()',parseInt(sessionTimeout) * 60 * 1000);

        //Session Warning
        function SessionWarning() {
            //minutes left for expiry
            var minutesForExpiry =  (parseInt(sessionTimeout) - 
				parseInt(sessionTimeoutWarning));
            var message = "Your session will expire in another " + minutesForExpiry + 
			" mins! Please Save the data before the session expires";
            alert(message);
            var currentTime = new Date();
            //time for expiry
            var timeForExpiry = timeOnPageLoad.setMinutes(timeOnPageLoad.getMinutes() 
				+ parseInt(sessionTimeout)); 

            //Current time is greater than the expiry time
            if(Date.parse(currentTime) > timeForExpiry)
            {
                alert("Session expired. You will be redirected to welcome page");
                window.location = "../Welcome.aspx";
            }
        }

        //Session timeout
        function RedirectToWelcomePage(){
            alert("Session expired. You will be redirected to welcome page");
            window.location = "../Welcome.aspx";
        }
  </script>	

In this approach, the user will be warned about the session timeout. If user does not save or do any post back, he would be redirected to the login or home page, once the session interval time expires.

3. Extend User Session

 <script language="javascript" type="text/javascript">
        var sessionTimeoutWarning = 
	"<%= System.Configuration.ConfigurationSettings.AppSettings
	["SessionWarning"].ToString()%>";
        var sessionTimeout = "<%= Session.Timeout %>";
        var timeOnPageLoad = new Date();
        var sessionWarningTimer = null;
        var redirectToWelcomePageTimer = null;
        //For warning
        var sessionWarningTimer = setTimeout('SessionWarning()', 
				parseInt(sessionTimeoutWarning) * 60 * 1000);
        //To redirect to the welcome page
        var redirectToWelcomePageTimer = setTimeout('RedirectToWelcomePage()',
					parseInt(sessionTimeout) * 60 * 1000);

        //Session Warning
        function SessionWarning() {
            //minutes left for expiry
            var minutesForExpiry =  (parseInt(sessionTimeout) - 
					parseInt(sessionTimeoutWarning));
            var message = "Your session will expire in another " + 
		minutesForExpiry + " mins. Do you want to extend the session?";

            //Confirm the user if he wants to extend the session
            answer = confirm(message);

            //if yes, extend the session.
            if(answer)
            {
                var img = new Image(1, 1);
                img.src = 'KeepAlive.aspx?date=' + escape(new Date());

                //Clear the RedirectToWelcomePage method
                if (redirectToWelcomePageTimer != null) {
                    clearTimeout(redirectToWelcomePageTimer);
                }
   	       //reset the time on page load
                timeOnPageLoad =  new Date();
                sessionWarningTimer = setTimeout('SessionWarning()', 
				parseInt(sessionTimeoutWarning) * 60 * 1000);
                //To redirect to the welcome page
                redirectToWelcomePageTimer = setTimeout
		('RedirectToWelcomePage()',parseInt(sessionTimeout) * 60 * 1000);
            }

            //*************************
            //Even after clicking ok(extending session) or cancel button, 
	   //if the session time is over. Then exit the session.
            var currentTime = new Date();
            //time for expiry
            var timeForExpiry = timeOnPageLoad.setMinutes(timeOnPageLoad.getMinutes() + 
				parseInt(sessionTimeout)); 

            //Current time is greater than the expiry time
            if(Date.parse(currentTime) > timeForExpiry)
            {
                alert("Session expired. You will be redirected to welcome page");
                window.location = "../Welcome.aspx";
            }
            //**************************
        }

        //Session timeout
        function RedirectToWelcomePage(){
            alert("Session expired. You will be redirected to welcome page");
            window.location = "../Welcome.aspx";
        }
</script>   

In this approach, the user will be warned about the session timeout and provides the ability to extend user session. If the user confirms to extend the session, it gets extended. If user confirms after the session expiry timeout limit, even then the user will be logged out. Following lines of code are used to extend the user session. Where 'KeepAlive.aspx is a dummy page in the website.

var img = new Image(1, 1); 
img.src = 'KeepAlive.aspx?date=' + escape(new Date()); 

Note: In all the above scenarios, I am assuming SetTimeout method and session related variables will be reset whenever there is a post back. This may not work 100%, when there could be partial rendering and the SetTimeout method and session related variables may not be reset. All files are in the Samples folder.

References

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Manjunath Shrikantiah
Architect
India India
9+ plus years of experience in IT industry. This includes experience in architecting, designing and developing solutions on Web and desktop application platforms

Comments and Discussions

 
GeneralGreat Post !! PinmemberDanish Islam24-Jun-14 21:21 
QuestionGreat contribution Pinmembergefahr1-Feb-14 15:05 
AnswerRe: Great contribution PinmemberManjunath Shrikantiah2-Feb-14 22:57 
AnswerRe: Great contribution PinmemberScott Perry10-Mar-14 5:45 
QuestionExtending the session - How does it work? PinmemberCiaran Gallagher8-Dec-13 22:45 
QuestionInput Extend time from user PinmemberSunny Setia16-Jul-13 0:05 
GeneralMy vote of 5 PinmemberSunny Setia15-Jul-13 23:58 
QuestionSession Expire when no button is clicked Pinmembernandhy0431-May-13 11:08 
QuestionAdding Yes/No buttons PinmemberMember 998163212-Apr-13 9:46 
GeneralMy vote of 5 PinmemberNoName_ark26-Mar-13 9:39 
GeneralMy vote of 5 PinmemberMember 97600722-Nov-12 20:36 
QuestionNeed help to understand few line of code and its meaning for session expiry PinmemberTridip Bhattacharjee15-Oct-12 8:34 
Questionregarding session management PinmemberTridip Bhattacharjee4-Oct-12 20:58 
QuestionFails if opens new tab PinmemberSteve Montgomery7-Sep-12 1:01 
Generalimage(1,1) what is that.. please explain... Pinmemberpereubu12319-Jul-12 1:24 
GeneralRe: image(1,1) what is that.. please explain... PinmemberManjunath Shrikantiah19-Jul-12 3:31 
GeneralRe: image(1,1) what is that.. please explain... Pinmemberpereubu12320-Jul-12 3:42 
Questionreset the session Pinmemberwissam bishouty26-Apr-12 22:16 
AnswerRe: reset the session PinmemberManjunath Shrikantiah26-Apr-12 22:27 
GeneralRe: reset the session Pinmemberwissam bishouty26-Apr-12 23:02 
GeneralRe: reset the session PinmemberManjunath Shrikantiah27-Apr-12 1:37 
GeneralRe: reset the session Pinmemberwissam bishouty27-Apr-12 1:59 
GeneralRe: reset the session Pinmemberwissam bishouty27-Apr-12 23:15 
Questionerror Pinmembericelated13-Mar-12 18:58 
AnswerRe: error PinmemberManjunath Shrikantiah13-Mar-12 19:03 
QuestionAlert Session Time out in ASP.NET PinmemberRachana Patel28-Feb-12 8:08 
AnswerRe: Alert Session Time out in ASP.NET PinmemberManjunath Shrikantiah28-Feb-12 17:39 
GeneralRe: Alert Session Time out in ASP.NET PinmemberRachana Patel2-Mar-12 10:59 
GeneralRe: Alert Session Time out in ASP.NET PinmemberManjunath Shrikantiah12-Mar-12 20:33 
GeneralRe: Alert Session Time out in ASP.NET PinmemberRachana Patel28-Mar-12 7:51 
GeneralRe: Alert Session Time out in ASP.NET PinmemberManjunath Shrikantiah29-Mar-12 1:51 
GeneralMy vote of 5 PinmemberSandeep Ramani17-Aug-11 22:31 
GeneralMy vote of 5 Pinmembersaxenaabhi627-Jul-11 23:41 
QuestionOther soluion PinmemberMember 179304118-Jul-11 7:38 
AnswerRe: Other soluion PinmemberManjunath Shrikantiah18-Jul-11 23:28 

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Web04 | 2.8.140709.1 | Last Updated 27 Jul 2011
Article Copyright 2011 by Manjunath Shrikantiah
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