C# step by step 学习笔记8 CHAPTER 9 使用枚举和结构创建值类型

本章内容

1. 声明一个枚举类型
2. 创建并使用一个枚举类型
3. 声明一个结构类型
4. 创建并使用一个结构类型
5. 解释结构和类之间行为的差别

        enum Season { Spring, Summer, Fall, Winter }

        You can assign a value that is defined by the enumeration only to an enumeration variable.

        Note:As you can with all value types, you can create a nullable version of an enumeration variable by using the ? modifier. You can then assign the null value, as well the values defined by the enumeration, to the variable: Season? colorful = null;

        All enumeration literal names are scoped by their enumeration type. This is useful because it allows different enumerations to coincidentally contain literals with the same name.

        Many of the standard operators you can use on integer variables can also be used on enumeration variables (except the bitwise and shift operators, which are covered in Chapter 16, “Using Indexers”). For example, you can compare two enumeration variables of the same type for equality by using the equality operator (==), and you can even perform arithmetic on an enumeration variable (although the result might not always be meaningful!).

        Internally, an enumeration type associates an integer value with each element of the enumeration. By default, the numbering starts at 0 for the first element and goes up in steps of 1.