IComparable的 <T> 继承还是接口？

Question

在下面的示例中，据我了解，IComparable方法CompareTo用作基本方法。 我想知道在类中实现接口方法（CompareTo）是否是强制性的吗？ 下面的示例未执行此操作。 刚用过。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace test
{
public class MyClass<T> where T : IComparable<T>
{
    public void GetBiggerValue(T Value1, T Value2)
    {
        if (Value1.CompareTo(Value2) > 0)
        {
            Console.WriteLine("{0} is bigger than {1}", Value1, Value2);
        }

        if (Value1.CompareTo(Value2) == 0)
        {
            Console.WriteLine("{0} is equal to {1}", Value1, Value2);
        }

        if (Value1.CompareTo(Value2) < 0)
        {
            Console.WriteLine("{0} is smaller than {1}", Value1, Value2);
        }
    }
}

class Program
{
    static void Main(string[] args)
    {
        Program p = new Program();

        MyClass<int> mcInt = new MyClass<int>();
        MyClass<string> mcString = new MyClass<string>();

        mcInt.GetBiggerValue(124, 126);             //126          

        Console.ReadKey();
    }
}
}

Answer 1

在

 public class MyClass<T> where T : IComparable<T>

MyClass类型不实现（或“继承”） IComparable<T>但它要求其Type Parameter T实现。

在您的测试用例中，类型int和string是满足此约束的类型。

Answer 2

必须实现IComparable<T>是T ，但不是MyClass<T> IComparable<T> ：

 where T : IComparable<T> // <- It is T that's restricted

在您的情况下：

 // T == int; int is comparable (implements IComparable<int>)
 MyClass<int> mcInt = ...

 // T == string; string is comparable (implements IComparable<string>)
 MyClass<string> mcString = ...

如果放置MyClass<int[]> （ int[]不实现IComparable<int[]> ），则会出现编译时错误。

编辑：当前的实现存在一些问题：

// Technically, you don't want any MyClass<T> instance
//TODO: change into static: public static void GetBiggerValue(T Value1, T Value2
public void GetBiggerValue(T Value1, T Value2) {
  //DONE: Value1 can well be null; Value1.CompareTo(...) will throw exception then
  //DONE: CompareTo can be expensive, compute it once
  int compare = (null == Value1) 
    ? (null == Value2 ? 0 : -1) // null equals to null, but less any other value
    : Value1.CompareTo(Value2);

  // A shorter alternative is 
  // int compare = Comparer<T>.Default.Compare(Value1, Value2);

  //DONE: if ... else if is more readable construction in the context 
  if (compare > 0) 
    Console.WriteLine("{0} is bigger than {1}", Value1, Value2);
  else if (compare < 0)
    Console.WriteLine("{0} is smaller than {1}", Value1, Value2);
  else  
    Console.WriteLine("{0} is equal to {1}", Value1, Value2);
}