Value Types and Reference Types

Value Types

• Allocated on the stack.
• Value type variables are local copies.
• Value types are deived from System.ValueType
• Values types are always sealed and cannot be extended.
• Variables are passed by value( copy of the variable is passed into the called function )
• Value types are never placed onto the heap and therefore do not need to be finalized.
• The variable of this type die when they fall out of the defining scope.

Reference Types

• Allocated on the managed heap
• Reference type variables are pointing to the memory occupied by the allocated instance
• Variables are passed by reference( address of the variable is passed to the called function )
• The variable of this type die when they are garbage collected.

Nullable Types
Value types can never be assigned the value of null.

the ? suffix notation is a shorthand for creating an instance of the generic System.Nullable structure type.
?? operator allows o assign a value to a nullable type if the retrieved value is in fact null.