How to know if a session has been set

Question

In php i used to use

session_start();
if(isset(SESSION["user"]))
{
   //session is set
}
els{
    // there is no session 
}

but do i do that in asp.net? I mean. What code can tells wheather a session is set or not

ex: asp.net c#

//login.aspx
SESSION["USER"];

//user_profile.aspx
if(SESSION["USER"])// how do i validate that??
{

}

Answer 1

SESSION["USER"]; //this should throw an error since it's not setting a value and not a method.

You can test your session values like this:

if (Session["USER"] != null)
{
    //do something interesting
}

Answer 2

If you want to check for the existance of a session variable this will be fine:

if(Session["USER"] != null)
{
    //If you get here a session variable "USER" exists...
}

Though it is possible to disable session state in an asp.net application it is very rare to see that.

Answer 3

From php side, cince isset function

Determine if a variable is set and is not NULL.

Just check if this session null or not like:

if(Session["USER"] != null)
{
  // Do something
}