C#中如何为枚举类型添加描述方法【小技巧】

enum Color
{ 
  Red,
  Green,
  Blue
}

{ 
  enum-member-declarations,
  enum-member-declaration
}

 public enum Level
 {
  //Bad
  B = -1,

  //Normal
  N = 0,

  //Good
  G = 1,

  //Very Good 
  VG = 2
 }

 public static class LevelEnumExtension
 {
  public static string ToDescription(this Level level)
  {
   switch (level)
   {
    case Level.B:
     return "Bad";
    case Level.G:
     return "Good";
    case Level.N:
     return "Normal";
    case Level.VG:
     return "Very Good";
    default:
     return "Normal";
   }
  }
 }

 public enum Level
 {
  //Bad
  [Description("Bad")]
  B = -1,

  //Normal
  [Description("Normal")]
  N = 0,

  //Good
  [Description("Good")]
  G = 1,

  //Very Good 
  [Description("Very Good")]
  VG = 2
 }

 public static class EnumExtension
 {
  public static string ToDescription(this Enum val)
  {
   var type = val.GetType();

   var memberInfo = type.GetMember(val.ToString());
   
   var attributes = memberInfo[0].GetCustomAttributes(typeof(DescriptionAttribute), false);

   if (attributes == null || attributes.Length != 1)
   {
    //如果没有定义描述，就把当前枚举值的对应名称返回
    return val.ToString();
   }

   return (attributes.Single() as DescriptionAttribute).Description;
  }
 }