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how to check whether session is expired or not in asp net


how to check whether session is expired or not in asp net  using -'c#,asp.net'

i ve specified the session time out in web.config file..when the session is timeout im not getting redirect to login page but i am geting error saying object reference not set to an instance.

can any one tell me the solution for this?
    

asked Sep 29, 2015 by kinnari
0 votes
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7 Answers

0 votes

You can check the HttpContext.Current.User.Identity.IsAuthenticated property which will allow you to know whether there's a currently authenticated user or not.

answered Sep 29, 2015 by devkumargupta
0 votes

I prefer not to check session variable in code instead use FormAuthentication. They have inbuilt functionlity to redirect to given LoginPage specified in web.config.

However if you want to explicitly check the session you can check for NULL value for any of the variable you created in session earlier as Pranay answered.

You can create Login.aspx page and write your message there , when session expires FormAuthentication automatically redirect to loginUrl given in FormAuthentication section


  
  

The thing is that you can't give seperate page for Login and SessionExpire , so you have to show/hide some section on Login.aspx to act it both ways.

There is another way to redirect to sessionexpire page after timeout without changing formauthentication->loginurl , see the below link for this : http://www.schnieds.com/2009/07/aspnet-session-expiration-redirect.html

answered Sep 29, 2015 by girisha
0 votes

Edit

you can use the IsNewSession property to check if the session was created on the request of the page

protected void Page_Load() 
{ 
   if (Context.Session != null) 
   { 
      if (Session.IsNewSession) 
      { 
         string cookieHeader = Request.Headers["Cookie"]; 
         if ((null != cookieHeader) && (cookieHeader.IndexOf("ASP.NET_SessionId") >= 0)) 
         { 
            Response.Redirect("sessionTimeout.htm"); 
         } 
      } 
   } 
}

pre

Store userid in session variable when user log in to website and check on your master page or created base page form whihc other page get inherits... and in page load check that userid is present or not if not than redirect to login page

if(Session["Userid"]==null)
{
  //session expire redirect to login page 
}
answered Sep 29, 2015 by tseetha
0 votes

Use Session.Contents.Count:

if (Session.Contents.Count == 0)
{
    Response.Write(".NET session has Expired");
    Response.End();
}
else
{
    InitializeControls();
}

The code above assumes that you have at least one session variable created when the user first visits your site. If you don't have one then you are most likely not using a database for your app. For your case you can just manually assign a session variable using the example below.

protected void Page_Load(object sender, EventArgs e)
{
    Session["user_id"] = 1;
}

Best of luck to you!

answered Sep 29, 2015 by abhi
0 votes

I use the @Adi-lester answer and add some methods.

Method to verify if Session is Alive

public static void SessionIsAlive(HttpSessionStateBase Session)
{
    if (Session.Contents.Count == 0)
    {
        Response.Redirect("Timeout.html"); 
    }
    else
    {
        InitializeControls();
    }
}

Create session var in Page Load

protected void Page_Load(object sender, EventArgs e)
{
    Session["user_id"] = 1;
}

Create SaveData method (but you can use it in all methods)

protected void SaveData()
{
    // Verify if Session is Alive
    SessionIsAlive(Session);

    //Save Data Process
    // bla
    // bla
    // bla
}
answered Sep 29, 2015 by gauravsinghal83
0 votes

this way many people detect session has expired or not. the below code may help u.

protected void Page_Init(object sender, EventArgs e)
    {
        if (Context.Session != null)
        {
            if (Session.IsNewSession)
            {
                HttpCookie newSessionIdCookie = Request.Cookies["ASP.NET_SessionId"];
                if (newSessionIdCookie != null)
                {
                    string newSessionIdCookieValue = newSessionIdCookie.Value;
                    if (newSessionIdCookieValue != string.Empty)
                    {
                        // This means Session was timed Out and New Session was started
                        Response.Redirect("Login.aspx");
                    }
                }
            }
        }
    }
answered Sep 29, 2015 by vijayshukla80
0 votes

Here I am checking session values(two values filled in text box on previous page)

protected void Page_Load(object sender, EventArgs e)
{
    if (Session["sessUnit_code"] == null || Session["sessgrcSerial"] == null)
    {
        Response.Write("");
    }
    else
    {

        lblUnit.Text = Session["sessUnit_code"].ToString();
        LblGrcSr.Text = Session["sessgrcSerial"].ToString();
    }
}
answered Sep 29, 2015 by mtabakade

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