.NET 2.0 is missing an INullable interface! It's great that Nullable<T> was added to version 2 of .NET Framework, but why doesn't it implement an interface, where the interface has the HasValue property defined?

My problem is that I wanted to write some library code, where I wanted to be able to handle Nullable types. More precisely I wanted to know if the Nullable type had an value or not. In this situation I'm not interested in what type (T) it actually has, only if it has any value or not. Since I don't know T, I'm not able to make any type of cast and therefore had to use reflection to solve my problem. If Nullable<T> would have implemented an interface that exposed HasValue, this would not have been necessary.

I think that the lesson to be learned is that when you design your generic types, you should consider doing an interface that exposes methods and properties that are not in need of the specific type (T). This would make your code much easier to use in some situations and wouldn't bring much extra work to the table.