Question

How is it that you can access null nullable’s propery HasValue?
I looked to the compiled code, and it’s not a syntactic sugar.

Why this doesn’t throw NullReferenceException:

int? x = null;
if (x.HasValue)
{...}

Answer 1

That’s because int? is short for Nullable<int> which is a value type, not a reference type – so you will never get a NullReferenceException.

The Nullable<T> struct looks something like this:

public struct Nullable<T> where T : struct
{
    private readonly T value;
    private readonly bool hasValue;
    //..
}

When you assign null there is some magic happening with support by the compiler (which knows about Nullable<T> and treats them special in this way) which just sets the hasValue field to false for this instance – which is then returned by the HasValue property.