c# - 实现 IComparable 接口(interface)

Question

我现在正在阅读《c#6.0 in a Nutshell》这本书，下面的代码主题是“实现 IComparable 接口(interface)”。

我没有得到一些东西:

1. 为什么 IComparable.CompareTo 在那里显式实现？
2. 如果这只是 CompareTo 的另一个隐式重载(一个隐式int CompareTo(Note other), 另一种隐式int CompareTo(object other) ?

public struct Note : IComparable<Note>, IEquatable<Note>, IComparable
{
   int _semitonesFromA;
   public int SemitonesFromA { get { return _semitonesFromA; } }

   public Note (int semitonesFromA)
   {
     _semitonesFromA = semitonesFromA;
   }

   public int CompareTo (Note other) // Generic IComparable<T>
   {
   if (Equals (other)) return 0; // Fail-safe check
   return _semitonesFromA.CompareTo (other._semitonesFromA);
   }

   int IComparable.CompareTo (object other) // Nongeneric IComparable
   {
   if (!(other is Note))
   throw new InvalidOperationException ("CompareTo: Not a note");
   return CompareTo ((Note) other);
   }

   public static bool operator < (Note n1, Note n2)
     => n1.CompareTo (n2) < 0;

   public static bool operator > (Note n1, Note n2)
     => n1.CompareTo (n2) > 0;

   public bool Equals (Note other) // for IEquatable<Note>
     => _semitonesFromA == other._semitonesFromA;

   public override bool Equals (object other)
   {
   if (!(other is Note)) return false;
   return Equals ((Note) other);
   }

   public override int GetHashCode() => _semitonesFromA.GetHashCode();
   public static bool operator == (Note n1, Note n2) => n1.Equals (n2);
   public static bool operator != (Note n1, Note n2) => !(n1 == n2);
}

Answer 1

您可以隐式实现IComparable，是的。但从根本上说，您想要阻止用户将 Note 与另一个 Note 以外的任何内容进行比较。如果 IComparable，您可能有遗留用法，但如果有任何人直接知道 Note 类，您不希望允许:

Note note = new Note();
Other other = new Other();
int result = note.CompareTo(other);

您知道这总是会引发异常，那么为什么要允许它呢？基本上，将非通用 IComparable 接口(interface)视为“有点遗留”(有有效用途，但是......)并通过明确实现它来阻止任何人使用它。