Problem with App_Code folder

I have a C# ASP.NET web application.  Having reading about the App_Code folder I decided it is what I need and went ahead and create one.  I then proceeded to place .cs files in there with the classes I want to access throughout my application, however...

All the the classes I write in the App_Code folder don't seem to be accessing any of the namespaces I need (such as System.Web.UI.Page) and even after referincing them the intellisense refuses to see it.

In addition I cannot access any of the methods within the App_Code folder from within anywhere else in my application (I have double-checked namespaces are correct).

In case it helps I have included the source for the only .cs file I have stored in the App_Code folder:
using System;
using System.Data;
using System.Configuration;
using System.Web;
...