Is interface is value type or Reference type?

Thanks for the support, Javeed :)

If you think about it, it's just not possible for a type to be both a reference type and a value type - it has to be one or the other.

This is because memory needs to be allocated in advance for all variables and the CLR therefore needs to know how much memory to allocate.

A value type could in theory be any size (though it's normally no more than 16 bytes) and the variable actually needs to hold an instance of the value type.

However, a variable of a reference type contains a pointer, which will either be 4 bytes (32 bit system) or 8 bytes (64 bit system) long, to where the actual instance is stored on the heap. The pointer could also be null (all bytes zero) if the variable doesn't currently refer to an instance.

To have a unified type system, MS therefore came up with the idea of 'boxing' value types on the heap so that an object or interface variable could contain a reference to a boxed object rather than the value type instance itself.

Of course, if you call the GetType() method  - which all types inherit from System.Object - this gives you the runtime type of the object (i.e. what it really is) rather than its compile time type.