using System;

​

namespace EnumExtension {

  public static class Extensions {

​

    public static bool weekEnd(this DayOfWeek day) {

      return day == DayOfWeek.Sunday || day == DayOfWeek.Saturday;

    }

  }

​

  public enum DayOfWeek {

    Sunday,

    Monday,

    Tuesday,

    Wednesday,

    Thursday,

    Friday,

    Saturday,

  }

​

  public class EnumTypeEx {

​

    public static void Main() {

      var aDay = DayOfWeek.Wednesday;

      Console.WriteLine($"{aDay}({typeof(DayOfWeek)})：{(int)aDay}  -- {aDay.weekEnd()}");

      Console.WriteLine();

​

      for (DayOfWeek day = 0; DayOfWeek.IsDefined(day); day++) {

        Console.WriteLine($"{day}: {day.weekEnd()}");

      }

      Console.WriteLine();

      foreach(DayOfWeek day in Enum.GetValues(typeof (DayOfWeek))) {

        Console.WriteLine($"{day}: {day.weekEnd()}");

      }

    }

  }

}