Enum แบบ Flags และการรวมค่าระดับบิต

อีนัมแบบแฟล็ก

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2, Execute = 4 }
class Program {
    static void Main() {
        Access a = Access.Read | Access.Write;
        Console.WriteLine(a);
    }
}

เลขยกกำลังของสอง

using System;

[Flags]
enum Perm { Read = 1, Write = 2, Delete = 4, Share = 8 }
class Program {
    static void Main() {
        Console.WriteLine((int)Perm.Share);
    }
}

การรวมค่าด้วย OR

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2, Execute = 4 }
class Program {
    static void Main() {
        Access a = Access.Read | Access.Execute;
        Console.WriteLine((int)a);
    }
}

การตรวจสอบด้วย HasFlag

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2, Execute = 4 }
class Program {
    static void Main() {
        Access a = Access.Read | Access.Write;
        Console.WriteLine(a.HasFlag(Access.Write));
        Console.WriteLine(a.HasFlag(Access.Execute));
    }
}

การตรวจสอบด้วย AND ระดับบิต

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2 }
class Program {
    static void Main() {
        Access a = Access.Read | Access.Write;
        bool canWrite = (a & Access.Write) != 0;
        Console.WriteLine(canWrite);
    }
}

การนำแฟล็กออก

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2, Execute = 4 }
class Program {
    static void Main() {
        Access a = Access.Read | Access.Write;
        a &= ~Access.Write;
        Console.WriteLine(a);
    }
}

การเพิ่มแฟล็ก

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2, Execute = 4 }
class Program {
    static void Main() {
        Access a = Access.Read;
        a |= Access.Execute;
        Console.WriteLine(a);
    }
}

การสลับแฟล็ก

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2 }
class Program {
    static void Main() {
        Access a = Access.Read;
        a ^= Access.Write;
        Console.WriteLine(a);
        a ^= Access.Write;
        Console.WriteLine(a);
    }
}

เหตุผลที่ [Flags] มีความสำคัญ

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2, Execute = 4 }
class Program {
    static void Main() {
        Access a = Access.Read | Access.Execute;
        Console.WriteLine(a);
    }
}

การกำหนดสมาชิกแบบรวม

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2, Execute = 4, All = Read | Write | Execute }
class Program {
    static void Main() {
        Console.WriteLine((int)Access.All);
    }
}

การใช้แฟล็กในทางปฏิบัติ

using System;

[Flags]
enum Feature { None = 0, Dark = 1, Beta = 2, Sync = 4 }
class Program {
    static void Main() {
        Feature f = Feature.Dark | Feature.Sync;
        Console.WriteLine(f.HasFlag(Feature.Beta));
    }
}

ตรวจสอบความเข้าใจ

สรุปทบทวน