Ok, so, my visual studio is broken. I say this NOT prematurely, as it was my first response to see where I had messed up in my code. When I add controls to the page I can\'t
This can also happen if the Inherits property on the source page doesn't match the class name in the code behind. Generally speaking, this would probably only happen if you copy/pasted a .ascx/.aspx file and forgot to update it.
Example:
<%@ Control AutoEventWireup="false" CodeBehind="myControl.ascx.vb" Inherits="myProject.myWrongControl" %>
The the code behind class:
Partial Public Class myControl