How to use ASP.NET Session State in an HttpHandler?

Question

I have an HttpHandler that is run on a client page (cross domain, not on our IIS server, etc) and when they click on our embedded link it fires off the Handler on our server

Answer 1

Have your HttpHandler implement the IRequiresSessionState interface. It will enable session state use. IRequiresSessionState can be found in the System.Web.SessionState namespace.

Answer 2

I think you have to implement the empty interface IReadOnlySessionState, so the context will be loaded.

edit to add:

According to Michael Morton's answer, you can also implement IRequiresSessionState, which will give you write access also to the Session object

Answer 3

using System; 
using System.Web;
using System.Web.SessionState;
public class DownloadHandler : IHttpHandler, IReadOnlySessionState
{
   public bool IsReusable { get { return true; } }

   public void ProcessRequest(HttpContext context)
   {
       context.Response.Write(context.Session["kmx"]);
   }
}

Answer 4

try using the current context...

System.Web.HttpContext.Current.Session