How to access session variables from any class in ASP.NET?

(Updated for completeness)
You can access session variables from any page or control using Session["loginId"] and from any class (e.g. from inside a class library), using System.Web.HttpContext.Current.Session["loginId"].

But please read on for my original answer...

I always use a wrapper class around the ASP.NET session to simplify access to session variables:

public class MySession{    // private constructor    private MySession()    {      Property1 = "default value";    }    // Gets the current session.    public static MySession Current    {      get      {        MySession session =          (MySession)HttpContext.Current.Session["__MySession__"];        if (session == null)        {          session = new MySession();          HttpContext.Current.Session["__MySession__"] = session;        }        return session;      }    }    // **** add your session properties here, e.g like this:    public string Property1 { get; set; }    public DateTime MyDate { get; set; }    public int LoginId { get; set; }}

This class stores one instance of itself in the ASP.NET session and allows you to access your session properties in a type-safe way from any class, e.g like this:

int loginId = MySession.Current.LoginId;string property1 = MySession.Current.Property1;MySession.Current.Property1 = newValue;DateTime myDate = MySession.Current.MyDate;MySession.Current.MyDate = DateTime.Now;

This approach has several advantages:

• it saves you from a lot of type-casting
• you don't have to use hard-coded session keys throughout your application (e.g. Session["loginId"]
• you can document your session items by adding XML doc comments on the properties of MySession
• you can initialize your session variables with default values (e.g. assuring they are not null)

Access the Session via the thread's HttpContext:-

HttpContext.Current.Session["loginId"]

The problem with the solution suggested is that it can break some performance features built into the SessionState if you are using an out-of-process session storage. (either "State Server Mode" or "SQL Server Mode"). In oop modes the session data needs to be serialized at the end of the page request and deserialized at the beginning of the page request, which can be costly. To improve the performance the SessionState attempts to only deserialize what is needed by only deserialize variable when it is accessed the first time, and it only re-serializes and replaces variable which were changed. If you have alot of session variable and shove them all into one class essentially everything in your session will be deserialized on every page request that uses session and everything will need to be serialized again even if only 1 property changed becuase the class changed. Just something to consider if your using alot of session and an oop mode.