【C#冷知識(shí)系列】（四）關(guān)于枚舉的冷知識(shí)

枚舉作為Flag使用

語法

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

注意事項(xiàng)

• 由于flag的本質(zhì)是使用或運(yùn)算進(jìn)行位運(yùn)算，所以枚舉值必須是能進(jìn)行或運(yùn)算的

應(yīng)用

• 權(quán)限管理

使用

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

WeekEnum week = WeekEnum.Sunday;
//添加一個(gè)星期
week = week | WeekEnum.Monday;
Console.WriteLine(week.ToString()); // 輸出Sunday, Monday

//去掉一個(gè)星期
week = week & ~WeekEnum.Sunday;
Console.WriteLine(week.ToString()); //輸出 Monday

//判斷是否有某個(gè)元素
obj.HasFlag()  // 返回True False

字符串轉(zhuǎn)化為枚舉

string day = "monday";
WeekEnum today = (WeekEnum)Enum.Parse(typeof(WeekEnum), day, true);
// 最后一個(gè)參數(shù)標(biāo)識(shí)字符串是否區(qū)分大小寫

修改枚舉的變量類型

xiupublic enum Color : short
{

}
// 可以變化為 byte short int 等類型

枚舉的遍歷

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);
    }
}