title: "Base class could not be loaded" - for no clear reason
body: <p>I'm using Visual C# 2008 <strong>Express</strong>. This is the first time I've had this error in years, the last time I had it was around the time I started programming.</p>
  <p>I have no idea what it actually means or why it suddenly came up, it seems rather ambiguous for what the error message says. All I know is that throughout my app, I inherit a lot of the main windows from a ThemedWindow class I came up with to give them a custom appearance, there are no errors in that code and everything was working 100% perfect 20 minutes ago.</p>
  <p>The error in full:</p>
  <blockquote>
  <p>Warning    12  The designer could not be shown for this file because none of the classes within it can be designed.  The designer inspected the following classes in the file:</p>
  <p>InheritingWindow --- The base class 'ThemedWindow' could not be loaded.  Ensure the assembly has been referenced and that all projects have been built.        0   0</p>
  </blockquote>
  <p>I get that for every form that inherits from ThemedWindow, and several other errors because the project won't build far enough for everything else to work.</p>
  <p>Just before this happened I updated the font on all forms and sub-controls, the project even built and ran after I did that, then this happened for absolutely no clear reason.</p>
  <p>I've tried the classic rebuild it, delete build files, reopen Visual Studio etc, but nothing seems to work at the moment.</p>
  <p>Does anyone know how to fix this?</p>