11.1.1 Default constructors

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博客介绍了值类型的默认构造函数，它是一个无参的公共实例构造函数，返回零初始化的实例。不同简单类型、枚举类型和结构体类型都有各自的默认值，默认构造函数用 new 操作符调用，且结构体不能显式声明无参构造函数，但可声明有参构造函数。

11.1.1 Default constructors
All 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 抃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 default
value and all reference type fields to null.
Like any other instance constructor, the default constructor of a value
type is invoked using the new
operator. [Note: For efficiency reasons, this requirement is not intended
to actually have the implementation
generate a constructor call. end note] [Example: In the example below,
variables i and j are both initialized
to 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 a
struct type to contain an explicit declaration of a parameterless
constructor. A struct type is however
permitted to declare parameterized instance constructors (?8.3.8).