I got strange compile-time error:
Project file must include the .NET Framework assembly 'WindowsBase, PresentationCore, PresentationFramework' in the reference list.
This project is aspnet mvc web application and all was fine for a long time.
After I added them Build went fine, but what could be a reason for this error?
You are using some type from the assemblies in your code. As a server side project this is almost certainly an error.
VS will normally give you an error immediately on entering the name of something for which it cannot find a definition so it seems odd that you got as far as a compile before noticing.
It was caused by addition of file with .xaml extension. By default, VS.NET try to complie it.
When I changed settings to BuildAction: none, copy to output: always I was able to remove those references.