Why does a `null` Nullable<T> have a hash code?

Question

Bit of a weird question...

But can anyone give me a justification for why this would be expected behaviour?

This just seems totally odd to me....

//Makes perfect sense object o = null; o.GetHashCode().Dump(); 

NullReferenceException: Object reference not set to an instance of an object.

//Seems very odd int? i = null; i.GetHashCode().Dump(); 

0

This obviously means:

int? zero = 0; int? argh = null;  zero.GetHashCode() == argh.GetHashCode(); //true 

Answer 1

The point here is that

int? i = null; 

does not create a variable i which is null, but (by performing an implicit cast) a Nullable<int> instance which does not have a value.
This means the object/instance is not null (and as Nullable<T> is a struct/value type it actually can't be null) and therefore has to return a hash-code.

This is also documented here:

The hash code of the object returned by the Value property if the HasValue property is true, or zero if the HasValue property is false.