IComparer 与 IComparable

        static void Main()
        {
            var people = new ArrayList();
            people.AddRange(new ArrayList
            {
                new Person{ Name = "Jone",Age = 18},
                new Person{ Name = "Tom",Age = 20},
                new Person{ Name = "Lily",Age = 15},
                new Person {Name = "July",Age = 25 }
            });
            Console.WriteLine("↓↓↓   Old   ↓↓↓");
            foreach (Person person in people)
            {
                Console.WriteLine($"person name:{person.Name} age:{person.Age}");
            }
            people.Sort(); //new PersonComparer()
            Console.WriteLine("↓↓↓   New   ↓↓↓");
            foreach (Person person in people)
            {
                Console.WriteLine($"person name:{person.Name} age:{person.Age}");
            }

            Console.ReadKey();
        }

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）

  class  Person :IComparable
    {
        public string Name { get; set; }

        public int Age { get; set; }
        public int CompareTo(object obj)
        {
            if (obj is Person person)
            {
                return this.Age - person.Age;
            }
            else
            {
                throw new ArgumentException("Object is not a Person");
            }
        }
    }

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）

class PersonComparer:IComparer
    {
        public int Compare(object x, object y)
        {
            if (x is Person personX && y is Person personY)
            {
                if (Object.ReferenceEquals(x,y))
                {
                    return 0;
                }
                int result = String.Compare(personX.Name, personY.Name, StringComparison.Ordinal);
                if (result == 0)
                {
                    result = personX.Age - personY.Age;
                }

                return result;
            }
            else
            {
                throw new ArgumentException("Object is not a Person");
            }
        }
    }