Reference types: The string type

Reference types

A reference type is a class type, an interface type, an array type, or a delegate type.

reference-type:
class-type
interface-type
array-type
delegate-type

class-type:
type-name
object
string

interface-type:
type-name

array-type:
non-array-type rank-specifiers

non-array-type:
type

rank-specifiers:
rank-specifier
rank-specifiers rank-specifier

rank-specifier:
[ dim-separators_opt ]

dim-separators:
,
dim-separators ,

delegate-type:
type-name

A reference type value is a reference to an instance of the type, the latter known as an object. The special value null is compatible with all reference types and indicates the absence of an instance.

Class types

A class type defines a data structure that contains data members (constants and fields), function members (methods, properties, indexers, events, operators, instance constructors, static constructors, and destructors), and nested types. Class types support inheritance, a mechanism whereby derived classes can extend and specialize base classes. Instances of class types are created using object-creation-expressions (‎7.5.10.1).

Class types are described in ‎10.

The object type

The object class type is the ultimate base class of all other types. Every type in C# directly or indirectly derives from the object class type.

The object keyword is simply an alias for the predefined System.Object class.

The string type

The string type is a sealed class type that inherits directly from object. Instances of the string class represent Unicode character strings.

Values of the string type can be written as string literals (‎2.4.4).

The string keyword is simply an alias for the predefined System.String class.

Interface types

An interface defines a contract. A class or struct that implements an interface must adhere to its contract. An interface may inherit from multiple base interfaces, and a class or struct may implement multiple interfaces.

Interface types are described in ‎13.

Array types

An array is a data structure that contains a number of variables which are accessed through computed indices. The variables contained in an array, also called the elements of the array, are all of the same type, and this type is called the element type of the array.

Array types are described in ‎12.

Delegate types

A delegate is a data structure that refers to a static method or to an object instance and an instance method of that object.

The closest equivalent of a delegate in C or C++ is a function pointer, but whereas a function pointer can only reference static functions, a delegate can reference both static and instance methods. In the latter case, the delegate stores not only a reference to the method's entry point, but also a reference to the object instance for which to invoke the method.

Delegate types are described in ‎15.