Session Variable Null Reference Exception

Question

I am getting a Null Reference exception on the following line:

private void BindData()
{
         string username = Session["Username"].ToString();

This error is occurring when a user is logged in, stays idle for a few minutes and refreshed the page. I had the following in my Web.Config which I though might have caused the error but when I commented it, the error still occurred:

<sessionState timeout="20" />

Stack Trace:

    [NullReferenceException: Object reference not set to an instance of an object.]
   _1.PresentationLayer.WebPages.ViewItFaults.BindData() in C:\Users\Rcc\Desktop\Development\Ticketing system\1.PresentationLayer\WebPages\ViewItFaults.aspx.cs:26
   _1.PresentationLayer.WebPages.ViewItFaults.Page_Load(Object sender, EventArgs e) in C:\Users\Rcc\Desktop\Development\Ticketing system\1.PresentationLayer\WebPages\ViewItFaults.aspx.cs:19
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +51
   System.Web.UI.Control.OnLoad(EventArgs e) +92
   System.Web.UI.Control.LoadRecursive() +54
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +772

How have you confirmed that there is a value with that key in the session? — Richard, Nov 18 '14 at 13:32
@Richard, yes there is a value which is set when the user loggs in. The page works, the error only occurs after being idle for a few minutes — rikket, Nov 18 '14 at 13:36
But how are you confirming this (just because it is set does not mean something else, including session timeout, cannot remove it)? — Richard, Nov 18 '14 at 13:37
Almost all cases of `NullReferenceException` are the same. Please see "[What is a NullReferenceException in .NET?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-in-net)" for some hints. — John Saunders, Nov 18 '14 at 13:50

score 0 · Answer 1 · answered Nov 18 '14 at 13:37

0

When you comment out that line, ASP.net uses the default timeout, which is 20. So, commenting that line doesn't change anything. If you want a session to last longer, specify a higher timeout. 525600 minutes is the longest possible timeout (1 year)

<sessionState timeout="525600" />

On a side note, make sure your exception is handled correctly, avoid yellow screens of death at all costs

answered Nov 18 '14 at 13:37

cpacheco

186
9

http://msdn.microsoft.com/en-us/library/system.web.sessionstate.httpsessionstate.timeout(v=vs.110).aspx – cpacheco Nov 18 '14 at 13:38
500 minutes is about eight and half hours, it is no where close to a year. – Richard Nov 18 '14 at 13:38
typo. Will edit to correct answer. I meant 500000, but it turned out to be exactly 1 year (525600) – cpacheco Nov 18 '14 at 13:39

Session Variable Null Reference Exception

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