I was given a webproject written with aspx/c#. When I loaded it into Visual Studio 2010, I got many error telling me that some controls in the code-behind files do not exist in the current context.
I checked for the common pitfalls, like wrong code-behind file name, missing runat-attribute, restart VS, reload project, yet nothing resolves the error.
What else can I do to check where the problem is?
Cudos to @03Usr the following link brought the answer:
ASP.NET controls cannot be referenced in code-behind in Visual Studio 2008
Deleting all designer files and converting the project als web application brought the designer files back, effectively making the controls referenceable again.