Question mark on a type

Question

I've used this quite innocently for a while now without actually knowing much about it, but basically it's:

Private _SomeFieldDate As DateTime?

or...

Private _SomeFieldInt As Int32?

I realise that the question mark on the end allows the definition of a Null or rather Nothing value to be assigned to the field, but what exactly happens here, and what is the term for this question mark?

(PS: I did try looking for this on SO but couldn't find it; if this has previously been posted then would you mind popping a link to the post in an answer, please?)

Answer 1

It's called a nullable and the question mark is short for

Nullable<T>

More info on msdn