How to throw compilation error from an attribute?

Question

there are attributes in .NET (e.g. ObsoleteAttribute) which are able to prevent compilation or at least throw compile time warnings depending on their configuration.

Answer 1

Obsolete attribute is "compiler magic" - you can't do something like this on your own without modifying the compiler. However, as always, there are workarounds - e.g. take a look at this and this thread.