There were several breaking changes (fixes) in C# 3 from C# 2. One is the ability to attribute a member override with ObsoleteAttribute without also attributing it the virtual member in the base class. For example, the following will compile without error In C# 2 (Visual Studio 2005/.NET 2.0): using...
My latest Visual C# Developer Center Article Inferred Typing with Factory Methods as Extension Methods is now online.