VS.Net and ASP.Net ’Helpful’ problem

We have a problem with Visual Studio.Net trying to be helpful and getting it wrong.

Basically we have created an abstract page class that contains common initialisation code, including a common control for html header information, and a sidebar, and the data sources that bind to the side bar to create the common menu system.

This works great and we are able to create multiple pages that all inherit the common structure.  The problem is that because the controls are placed in the html of the actual page, visual studio.net, in trying to be helpful, places definitions for the controls into the child pages automatically.  This causes errors because it clashes with the parent abstact classes definitions.  Does anyone know how to turn this 'helpful' feature off?