Guid == null should not be allowed by the compiler

Question

The behaviour described below is specific to .net-3.5 only

I just ran across the most astonishing behavior in the C# compiler;

I

Answer 1

The comparison is valid because the compiler converts the Guid to a Nullable and then it makes sense.

There is a bug report on the warning not being issued here.

See here here for a fuller explanation from Eric Lippert.