IComparer 与 IComparable

 1         static void Main()
 2         {
 3             var people = new ArrayList();
 4             people.AddRange(new ArrayList
 5             {
 6                 new Person{ Name = "Jone",Age = 18},
 7                 new Person{ Name = "Tom",Age = 20},
 8                 new Person{ Name = "Lily",Age = 15},
 9                 new Person {Name = "July",Age = 25 }
10             });
11             Console.WriteLine("↓↓↓   Old   ↓↓↓");
12             foreach (Person person in people)
13             {
14                 Console.WriteLine($"person name:{person.Name} age:{person.Age}");
15             }
16             people.Sort(); //new PersonComparer()
17             Console.WriteLine("↓↓↓   New   ↓↓↓");
18             foreach (Person person in people)
19             {
20                 Console.WriteLine($"person name:{person.Name} age:{person.Age}");
21             }
22 
23             Console.ReadKey();
24         }

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IComparable 是用于类对其的CompareTo方法进行实现，比较的对象包含自身，并且集合调用默认的Sort方法（个人理解是框架提供的默认比较方式）

 1   class  Person :IComparable
 2     {
 3         public string Name { get; set; }
 4 
 5         public int Age { get; set; }
 6         public int CompareTo(object obj)
 7         {
 8             if (obj is Person person)
 9             {
10                 return this.Age - person.Age;
11             }
12             else
13             {
14                 throw new ArgumentException("Object is not a Person");
15             }
16         }
17     }

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IComparer 是比较两个Object，是以比较器的形式存在的，并且集合调用Sort(new XxxComparer())方法（个人理解是框架对默认比较方式的扩展吧，用以满足特定的需求）

 1 class PersonComparer:IComparer
 2     {
 3         public int Compare(object x, object y)
 4         {
 5             if (x is Person personX && y is Person personY)
 6             {
 7                 if (Object.ReferenceEquals(x,y))
 8                 {
 9                     return 0;
10                 }
11                 int result = String.Compare(personX.Name, personY.Name, StringComparison.Ordinal);
12                 if (result == 0)
13                 {
14                     result = personX.Age - personY.Age;
15                 }
16 
17                 return result;
18             }
19             else
20             {
21                 throw new ArgumentException("Object is not a Person");
22             }
23         }
24     }

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