In a simple web application project, when adding new controls to an *.aspx file, Visual Studio generates a corresponding declaration of that same control in the *.designer.cs file. This works well (at least most of the time, as some might know) ;-)
Now, we have a more complex setup where we've decided to move all code-behind files to a separate project leaving the markup files (*.aspx and *.ascx) in the original project. Unfortunately, in this case the "magic" stops working.
My question: How does the magic in VS work which automates the generation/update/deletion of control declarations when markup and code-behind files reside in the same project and, more importantly, how I can achieve the same behaviour in the setup we have where those files are in separate projects?