session returns null object in asp.net

Question

I am developing asp.net web application in which i am using Session to store user related data.Though i am storing data in session object when i am trying to retrieve it gives me error :

Object reference not set to an instance of an object.

Setting session variable

somewhere in code behind of aspx page (myfile.aspx.cs)

HttpContext.Current.Session["ProjectID"] = Request.QueryString["Pid"].ToString();

Retrieving Session Variable

Normal Business Logic C# Class (Someclass.cs)

sProjectID = HttpContext.Current.Session["ProjectID"].ToString();

It gives me error on above line. It looks weird to me. can anyone explain this ?

Edit:

Call to class pass through generic handler (.ashx) page

Are you sure that putting variable into session is called before accessing in a class? — user2160375
– user2160375, Commented Jul 25, 2014 at 11:52

Community · Accepted Answer · 2017-05-23 12:09:20Z

2

If it is really the line of code you showed, that produces exception, it means your "Normal Business Logic" is running in a non-HttpRequest handling thread, where thing such as Context and Session are not available. Check that HttpContext.Current and HttpContext.Current.Session are not null.

Update:

After seeing your edit - to have access to Session, your handler must include IRequiresSessionState in its class declaration. See: HttpContext.Current.Session is null in Ashx file.

edited May 23, 2017 at 12:09

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answered Jul 25, 2014 at 12:38

Igor

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Comments

zblago · Accepted Answer · 2014-07-25 11:55:21Z

0

Can you reach in the debug mode line where you setting session values? If you can try to hit line after and inspect value in session by the key "ProjectID".

answered Jul 25, 2014 at 11:55

zblago

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3 Comments

Rajeev Kumar Over a year ago

You should put it as comment. This is not an answer

Shaggy Over a year ago

@Shark i did that. value goes in session varable

zblago Over a year ago

Is your business logic in separate assembly (project inside Visual Studio Solution). If it try to get a value from the session and pass like method parameter. Also, check answer from modiX.

Jai · Accepted Answer · 2014-07-25 12:04:13Z

0

You can't find any value in the session in the Debug mode.. Assign it to a reference variable like string and find whether it is returning a value..

and for a good practice check the session variable is null or not before assigning to any object..

answered Jul 25, 2014 at 12:04

Jai

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Comments

Martin Braun · Accepted Answer · 2014-07-25 12:06:56Z

Try setting the cookie this way:

HttpCookie cookie = HttpContext.Current.Request.QueryString["Pid"].ToString();
cookie.Expires = DateTime.Now.AddDays(7); // Set the expiration duration
HttpContext.Current.Response.Cookies.Set(cookie); // Set it to the response

And try getting the cookie this way on the next request:

string value = HttpContext.Current.Request.Cookies["Pid"] != null ? this.Page.Request.Cookies["Pid"].ToString() : null; // load it from request

Honestly, you should not try to receive your cookie in your business logic at all, as it has nothing to do with your website. Instead you should load the cookie in the UI (web) and pass the value as parameter to any function or property of your Someclass.cs in your business logic.

Take a look at the N-tier model and it's reasons to do so.

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