How to redirect to another page when session timeout in ASP.NET (when pages contain Ajax UpdatePanel)

Introduction

Session timeout in ASP.NET is such an important problem with web developer. When session ended, we run into some exceptional situations. There are also many solutions to deal with this problem on the Internet. But less of them have discussed about redirecting to other page when session timeout, especially when we work with Ajax UpdatePanel.

So, I suggest a way to do this.

Solution

My main idea is: 3 minutes before session gone, we will alert for the user for saving their data or make any postbacks. If user still does not do anything yet then 5 miliseconds before session gone, we will redirect the page to Login.aspx (or just refresh page by redirect to itself).

Using the code

Add to your Master page following code:

private void CheckSessionTimeout()
{
    string msgSession = 'Warning: Within next 3 minutes, if you do not do anything, '+
                        ' our system will redirect to the login page. Please save changed data.';
    //time to remind, 3 minutes before session end
    int int_MilliSecondsTimeReminder = (this.Session.Timeout * 60000) - 3 * 60000; 
    //time to redirect, 5 miliseconds before session end
    int int_MilliSecondsTimeOut = (this.Session.Timeout * 60000) - 5; 

    string str_Script = @"
            var myTimeReminder, myTimeOut; 
            clearTimeout(myTimeReminder); 
            clearTimeout(myTimeOut); " +
            "var sessionTimeReminder = " + int_MilliSecondsTimeReminder.ToString() + "; " +
            "var sessionTimeout = " + int_MilliSecondsTimeOut.ToString() + ";" +
            "function doReminder(){ alert('" + msgSession + "'); }" +
            "function doRedirect(){ window.location.href='login.aspx'; }" + @"
            myTimeReminder=setTimeout('doReminder()', sessionTimeReminder); 
            myTimeOut=setTimeout('doRedirect()', sessionTimeout); ";

     ScriptManager.RegisterClientScriptBlock(this.Page, this.GetType(), 
           "CheckSessionOut", str_Script, true);
}        

private void Page_Load(object sender, System.EventArgs e)
{
    this.CheckSessionTimeout();
}

If you do not want to redirect to login page, you can just refresh the page by replace by this code:

function doRedirect(){ window.location.href=window.location.href; }

If you do not use ScriptManager, you can replace with Page.RegisterClientScriptBlock(...)

Hope this help :)