How to load a type in parent-child website

I am developing a C# VS 2008 / SQL Server 2008 website. Although this same code compiles in the Project version, the website version does not compile. Many of their files are the same so I do not understand even where to look. The only compile error I get is:

Could not load type 开发者_如何学Go'DataMatch'

in my DataMatch.aspx file. Is the problem in my web.config file? How do websites differ from projects in VS? All four of these files reside in same directory.

Default.aspx file:

<%@ Page Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeFile="Default.aspx.cs"
    Inherits="AddFileToSQL" Title="Untitled Page" %>

Default.aspx.cs file:

using System.Data.SqlClient;
using System.Security.Principal;

namespace AddFileToSQL
{
    public partial class AddFileToSQL : System.Web.UI.Page
    {

...

DataMatch.aspx file:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="DataMatch.aspx.cs"
Inherits="DataMatch" %>

DataMatch.aspx.cs file:

using System.Web.UI.WebControls;
using AddFileToSQL;

public partial class DataMatch : AddFileToSQL
{

...

are you deploying it to a subdirectory on your website? if so the line:

MasterPageFile="~/Site.master"

might be unable to find the master file.