HttpContext.Current.Session is null in Ashx file

I saw some questions (Here and Here) but they do not answer my question. I am trying to call Ajax using "ajax.ashx" file, and in function to access Session. For some reason, the value of the Session object itself is null.

Use example:

Session = HttpContext.Current.Session // This is null

Or:

public virtual void ProcessRequest(HttpContext context)
{
    System.Web.SessionState.HttpSessionState Session = context.Session; 
    // This is null
}

In the Web.config:

<sessionState timeout="1800"></sessionState>

You must add on your handler the IRequiresSessionState on the declaration of it as:

public class YourHandleName : IHttpHandler, IRequiresSessionState 
{
...

by default the handlers are not connected with the session to keep them minimum, by adding the IRequiresSessionState you attach them with the session.