#31 – Value Types and Reference Types

All types in C#, whether built-in or user-defined custom types, can be categorized as either value types or reference types.

• Value types
  • Derive from System.ValueType (which derives from System.Object)
  • Allocated on the stack  (unless declared inside a reference type)
  • Value type variable contains value directly
  • Assignment makes a copy of the value
  • Passed by value (a copy is made)
  • Not garbage collected–die when they go out of scope
  • Either struct or enum
  • Sealed–can’t inherit from them

• Reference types
  • Derive from System.Object or another reference type
  • Allocated on the heap
  • Reference type variable contains a reference (pointer) to the object’s contents (or contains null)
  • Assignment creates a new reference to the original object
  • Passed by reference  (pointer to object is passed)
  • Garbage collected
  • One of: class, delegate, array or interface
  • Support inheritance