ERROR CS0234: The type or namespace name 'DataAccessHelper' does not exist in the namespace 'BCC' (are you missing an assembly reference?)

[li.eddie]

Hi All,
I'm new to ASP.NET and trying to create a Database application with
MS Visual Web Dev 2005. In my project, I wrote a generic abstract class
called DataAccessHelper.cs under App_Code folder which handles all the
Database related work, so all my WebForm classes can inherit from it
and consume its functions.
Inside the dev env, when I press F5, it launches the browser with
http://localhost:2739 and everything shows up as expected. However,
when I try to access it through a regular port 80, I get the following
error:

*********************************************
Compiler Error Message: CS0234: The type or namespace name
'DataAccessHelper' does not exist in the namespace 'BCC' (are you
missing an assembly reference?)

Source Error:
Line 12: namespace BCC
Line 13: {
Line 14: public partial class AddNewProgram : BCC.DataAccessHelper
Line 15: {
Line 16: int startTimeParam = 0;
*********************************************

I have searched the web for this error without much progress, but I did
get an impression that the helper class needs to be built into a
library and placed under application's root directory, so tried, but
still didn't work. This is the part where I'm very confused.

Can someone please help me with this?

Thanks in advance!