Is null in c# value type or reference type

Question

Originally I had this impression that NULL is reference type because it is assigned to references, then encountered this concept called nullable value types, this makes my theory in an awkward situation, so is NULL value type of reference type on earth ?

Answer 1

The C# specification is clear on this point: the null keyword represent an expression that has no type. It is neither reference type nor value type nor pointer type. However that expression is convertible to all of those types. There is no requirement that the compiler classify all expressions as having a type, and in fact it does not.

Now you might then ask at runtime what is the type of a null reference, what is the type of a null value of nullable value type, and what is the type of a null pointer. The answers are:

• a null reference does not have a type. If you have a box that can hold chocolates it is pointless to ask "what brand of chocolates are in this empty box?" A missing chocolate does not have a brand; a null reference does not have a type.

• similarly, the type of a null pointer is, again, not anything; null pointer values don't point to anything. If you have a piece of paper that has the address 1600 Pennsylvania Avenue on it, you can ask "what is the colour of the house at this address", and get the answer: white. If you have a blank piece of paper, asking what the colour of the house at that address is doesn't get you any useful answer.

• a null value of a nullable value type is a value of the nullable value type.

Answer 2

null isn't a type.

From msdn:

The null keyword is a literal that represents a null reference, one that does not refer to any object.

Nullable types are instances of the Nullable<T> struct which "Represents a value type that can be assigned null."