Detecting Session Timeout And Redirect To Login Page In ASP.NET

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Detecting Session Timeout and Redirect to Login Page in ASP.NET

In this example i'll explain how to detect session timeout and redirect to login page, session timeout occurs when user is idle for the time specified as Session timeout in web.config file using C# And VB.NET.

For this Example i've set time out value in web.config file to 1 minute.
1st Method


In web.config file, set the sessionstate mode to inproc and authentication mode to Forms
<system.web>
<compilation debug="true"/>
<authentication mode="Forms"/>
<sessionState mode="InProc" cookieless="false" timeout="1">
</sessionState>
</system.web>

I've created three pages in this example , one is login page , when session expires , i redirect to this page , one is navigation page where i'll check if session is valid or not , if it is valid than only user will see this page other wise he gets redirected to login page.

Add Global.asax class file in root of your application or website.
This method works only if Global.asax is present in application.

Write below mentioned code in Page_Init event of the page where we want to check for session timeout.

we can also put this code in in a class and inherit all pages of application from this class acting as base class for all pages to check for session timeout.

C# CODE
01protected void Page_Init(object sender, EventArgs e)
02    {
03        if (Context.Session != null)
04        {
05            if (Session.IsNewSession)
06            {
07                HttpCookie newSessionIdCookie = Request.Cookies["ASP.NET_SessionId"];
08                if (newSessionIdCookie != null)
09                {
10                    string newSessionIdCookieValue = newSessionIdCookie.Value;
11                    if (newSessionIdCookieValue != string.Empty)
12                    {
13                        // This means Session was timed Out and New Session was started
14                        Response.Redirect("Login.aspx");
15                    }
16                }
17            }
18        }
19    }

VB.NET CODE
01Protected Sub Page_Init(sender As Object, e As EventArgs)
02 If Context.Session IsNot Nothing Then
03  If Session.IsNewSession Then
04   Dim newSessionIdCookie As HttpCookie = Request.Cookies("ASP.NET_SessionId")
05   If newSessionIdCookie IsNot Nothing Then
06    Dim newSessionIdCookieValue As String = newSessionIdCookie.Value
07    If newSessionIdCookieValue <> String.Empty Then
08     ' This means Session was timed Out and New Session was started
09     Response.Redirect("Login.aspx")
10    End If
11   End If
12  End If
13 End If
14End Sub


2nd Method.
Code for Default.aspx 
<%@ Page Language="C#" AutoEventWireup="true"
CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC
"-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Button ID="btnSessionStart"
runat="server"
OnClick="btnSessionStart_Click"
Text="Start Session" /><br />
<br />
<br />
<asp:Button ID="btnCheck"
runat="server"
OnClick="btnCheck_Click"
Text="Check Session ID" />
<br />
<asp:TextBox ID="txtSession"
runat="server"
Width="266px">
</asp:TextBox><br />
<br />
<asp:Button ID="btnGO"
runat="server"
OnClick="btnGO_Click"
Text="Go to Other Page" />
<br />
<br />
</div>
</form>
</body>
</html>

And the code behind for this page is like
protected void btnSessionStart_Click
(object sender, EventArgs e)
{
Guid Session_id = Guid.NewGuid();
Session["SessionID"]
= Session_id.ToString();

}
protected void btnCheck_Click
(object sender, EventArgs e)
{
if (Session["SessionID"] != null)
txtSession.Text =
Session["SessionID"].ToString();
else
txtSession.Text =
"Session has expired";
}
protected void btnGO_Click
(object sender, EventArgs e)
{
Response.Redirect("Default2.aspx");
}

On the page where we want to check the session has timed out or not, we need to check it in the Page_Init event of the page , if session is not null than user will be able to go to the page other wise he will be redirected to login page.

In this page I've just put a button to go to home page
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Button ID="btnHome"
runat="server" OnClick="btnHome_Click"
Text="Home" /></div>
</form>
</body>
</html>

And the Code behind for this page is

protected void Page_Init(object sender, EventArgs e)
{
CheckSession();
}
protected void btnHome_Click(object sender, EventArgs e)
{
Response.Redirect("Default.aspx");
}

private void CheckSession()
{
if (Session["SessionID"] == null)
{
Response.Redirect("Login.aspx");
}

}

If we need to check this in all the pages of application than we can create a BaseClass and write the above mentioned code of CheckSession and Page_Init part and drive all ur pages from this class by typing BaseClassName in place of System.Web.UI.Page and it will check all pages for session timeout every time page is loaded

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