C# Language Specification - Willy .Net

C# LANGUAGE SPECIFICATIONfloating-point-type:floatdoubleenum-type:type-nameAll value types implicitly inherit from class object. It is not possible for any type to derive from a valuetype, and value types are thus implicitly sealed (§17.1.1.2).A variable of a value type always contains a value of that type. Unlike reference types, it is not possible fora value of a value type to be null, or to reference an object of a more derived type.Assignment to a variable of a value type creates a copy of the value being assigned. This differs fromassignment to a variable of a reference type, which copies the reference but not the object identified by thereference.11.1.1 Default constructorsAll value types implicitly declare a public parameterless instance constructor called the default constructor.The default constructor returns a zero-initialized instance known as the default value for the value type:• For all simple-types, the default value is the value produced by a bit pattern of all zeros:For sbyte, byte, short, ushort, int, uint, long, and ulong, the default value is 0.For char, the default value is '\x0000'.For float, the default value is 0.0f.For double, the default value is 0.0d.For decimal, the default value is 0.0m.For bool, the default value is false.• For an enum-type E, the default value is 0.• For a struct-type, the default value is the value produced by setting all value type fields to their defaultvalue and all reference type fields to null.Like any other instance constructor, the default constructor of a value type is invoked using the newoperator. [Note: For efficiency reasons, this requirement is not intended to actually have the implementationgenerate a constructor call. end note] [Example: In the example below, variables i and j are both initializedto zero.class A{void F() {int i = 0;int j = new int();}}end example]Because every value type implicitly has a public parameterless instance constructor, it is not possible for astruct type to contain an explicit declaration of a parameterless constructor. A struct type is howeverpermitted to declare parameterized instance constructors (§18.3.8).11.1.2 Struct typesA struct type is a value type that can declare constants, fields, methods, properties, indexers, operators,instance constructors, static constructors, and nested types. Struct types are described in §18.90