【C#冷知识系列】（四）关于枚举的冷知识

枚举作为Flag使用

语法

[Flags]
public enum Permission
{
    create = 1,
    read = 2,
    update = 4,
    delete = 8,
}

注意事项

• 由于flag的本质是使用或运算进行位运算，所以枚举值必须是能进行或运算的

应用

• 权限管理

使用

//初始化
WeekEnum week = (WeekEnum)127;
Console.WriteLine(week.ToString()); //输出 Sunday, Monday, Tuesday, Wendnesday, Thursday, Friday, Saturday

WeekEnum week = WeekEnum.Sunday;
//添加一个星期
week = week | WeekEnum.Monday;
Console.WriteLine(week.ToString()); // 输出Sunday, Monday

//去掉一个星期
week = week & ~WeekEnum.Sunday;
Console.WriteLine(week.ToString()); //输出 Monday

//判断是否有某个元素
obj.HasFlag()  // 返回True False

字符串转化为枚举

string day = "monday";
WeekEnum today = (WeekEnum)Enum.Parse(typeof(WeekEnum), day, true);
// 最后一个参数标识字符串是否区分大小写

修改枚举的变量类型

xiupublic enum Color : short
{

}
// 可以变化为 byte short int 等类型

枚举的遍历

public enum Suits
{
    Spades,
    Hearts,
    Clubs,
    Diamonds,
    NumSuits
}
private static void Main(string[] args)
{
    foreach (Suits suit in Enum.GetValues(typeof(Suits)))
    {
        Console.WriteLine((int)suit+ ":" + suit);
    }
}