web form call issue

In a C# 2010 web form application, I am having a problem with the master pages loading correctly. I am getting the following error: "Error1Could not load file or assembly 'MasterPages' or one of its dependencies. The system cannot find the file

specified.C:\sub\TestMasterPage.ascx1".
  To fix this problem I want to determine the hierarchy of the master pages so I can determine why this particular item is being

called.This way I will know the calling order of how this item is being called by;
  I know the following:

1.  I know this item is called by TestPage.aspx due to the code listed below:
<%@ language="c#" debug="true" trace="false" %>
<%@ Register TagPrefix="mp" namespace="Microsoft.Web.Samples.MasterPages" assembly="MasterPages" %>







2.  The namespace="Microsoft.Web.Samples.MasterPages" is calling this item based upon the statement above.
That code is in a member called: "MasterPages.cs".

Thus can you tell me what I need to do to solve this problem?