Object reference not set to an instance of an object.

Question

1.30/5 (3 votes)

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i got an error while running the code

on page1

C#

Session["UserAuthentication"] = username;

Response.Redirect("administrator.aspx?uid=" + username);

on page2

C#

protected void Page_Load(object sender, EventArgs e)
{
   string sName = (string)HttpContext.Current.Session["UserAuthentication"];
   if (sName != null)
   {
      Label1.Text = "Hi "+sName;
   }
}

Posted 28-Nov-11 19:04pm

Member 7909353

Updated 28-Nov-11 20:05pm

Prince Antony G

v4

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Comments

D K N T H 29-Nov-11 1:07am

in what line causes you an error?, please provide complete details

[no name] 29-Nov-11 1:10am

EDIT: added "pre" tag

4 solutions

Solution 1

Check first the value of username if it isn't null.

SQL

if(!String.IsNullOrEmpty(username))
{
   Response.Redirect("administrator.aspx?uid=" + username);
}
else
{
   //do not redirect
}

Please mark as answer and vote 5 if this solved your problem

Regards,
Eduard

Posted 28-Nov-11 19:09pm

Eduard Lu

Updated 28-Nov-11 19:12pm

v3

Solution 3

Try debugging this code to figure out where you are trying to access a property which is null.

Posted 28-Nov-11 19:14pm

Abhinav S

Solution 4

"Object reference not set to an instance of an object" is a generic error mostly throws by .NET if object is NULL.

as SA said check Session["UserAuthentication"]. can be null.
check code on Page2.

Posted 28-Nov-11 19:16pm

koolprasad2003

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Sergey Alexandrovich Kryukov · Accepted Answer · 2011-11-28T19:11:00

Solution 2

The expression Session["UserAuthentication"] can be null. In this case, in next line you are trying to calculate "Hi " + null which throws the exception.

Please, always run offending code under debugger before asking questions. It would make it all clear for you, so asking the question wouldn't be needed.

—SA

Posted 28-Nov-11 19:11pm

Sergey Alexandrovich Kryukov

Comments

Abhinav S 29-Nov-11 1:14am

My 5. Debugging - my point too.

Sergey Alexandrovich Kryukov 29-Nov-11 1:20am

Thank you, Abhinav. Debugging effort should be a prerequisite to the questions like this one.
--SA

koolprasad2003 29-Nov-11 1:16am

Yes. Session variable may be NULL. 5

Sergey Alexandrovich Kryukov 29-Nov-11 1:21am

Thank you, Prasad.
--SA

Uday P.Singh 29-Nov-11 1:19am

5ed, I don't know why they are reluctant to use the features of rich IDEs

Sergey Alexandrovich Kryukov 29-Nov-11 1:21am

Yes, and even reluctant just to review all the menus, see what's available. Hard to understand the lack of simple curiosity.
Thank you, Uday.
--SA