object reference error when using with session dataset

Question

Ive been using the following code for the last week and its worked no problem, then for some reason this morning its throwing:

System.NullReferenceException: Object reference not set to an instance of an object.

My code:

DataSet icanData = (DataSet)HttpContext.Current.Session["icanDataSession"];
if (!(icanData == null))
{
     return icanData;
}

The reason I'm using HttpContext.Current.Session is because its running in a class.

You will need to check `HttpContext.Current.Session == null`, not `HttpContext.Current == null`. If the session is null, that could point to other issues. — nick_w, Oct 12 '12 at 10:57
ive stopped it erroring by adding the following "if (HttpContext.Current != null && HttpContext.Current.Session != null)" however I dont think its storing the dataset in a session any more — andrew slaughter, Oct 12 '12 at 11:02
Which part of the page lifecycle are you doing this from? `Page_Load`? — nick_w, Oct 12 '12 at 11:33
Can you review my answer? I think it covers what you ended up doing to solve the problem. — nick_w, Oct 12 '12 at 12:53

score 1 · Answer 1 · answered Oct 12 '12 at 10:46

1

Looks like Session["icanDataSession"]; has been lost.

Where in your code does it get set? Maybe any sessions that were originally stored in IIS have been lost via an App Pool recycle.

answered Oct 12 '12 at 10:46

Darren

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if its not set i populate the dataset and then at the bottom i set it just before returning the dataset – andrew slaughter Oct 12 '12 at 10:57

score 0 · Accepted Answer · answered Oct 12 '12 at 10:49

0

Check session is null before cast session object to dataset

if(HttpContext.Current.Session["icanDataSession"]=!null)
{
  DataSet icanData = (DataSet)HttpContext.Current.Session["icanDataSession"];
  if (!(icanData == null))
   {
     return icanData;
   }
}
else 
{
return new Dataset();
}

answered Oct 12 '12 at 10:49

Anant Dabhi

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i havent really found a solution so i can't really accept any of the answers above – andrew slaughter Oct 12 '12 at 12:18
ive sorted it, it seems that if i create the instance of the dataset on the page as private it kills it. im sure your all shaking your heads now thinking "school boy" error but thanks for all your help – andrew slaughter Oct 12 '12 at 12:46

score 0 · Answer 3 · answered Oct 12 '12 at 10:49

0

I think, if this code is being called by an aspx.cs, then it will work fine. But if this is called by any stateless service, then it will throw error as you reported. Better to check if(HttpContext.Current != null) first..

answered Oct 12 '12 at 10:49

Anupam

1

ok ive used a bit of your code and a bit of Anant Dabhi's code so i now have this line "if (HttpContext.Current != null)" however im still getting the same error – andrew slaughter Oct 12 '12 at 10:55
it is being called by a .aspx file, what is wierd is that it has run fine all week – andrew slaughter Oct 12 '12 at 11:08

score 0 · Answer 4 · edited May 23 '17 at 12:18

0

You stated you were calling public static DataSet IcanData() at the top of your ASPX file. Instead, call that method from your Page_Load event. At the point in time where you are accessing the session it won't be available.

Information on why the session can be null can be found in this question: What should I do if the current ASP.NET session is null?

edited May 23 '17 at 12:18

Community

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answered Oct 12 '12 at 12:24

nick_w

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object reference error when using with session dataset

4 Answers4