ArrayList排序

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

namespace ArrySort
{
    class Program
    {
        static void Main(string[] args)
        {
            ArrayList arry = new ArrayList() { new Person() { Name = "apple", Age = 12 }, new Person() { Name = "dog", Age = 64 }, new Person() { Name = "cat", Age = 41 } };
            Console.WriteLine("排序之前");
            for (int i = 0; i < arry.Count; i++)
            {
                Console.WriteLine(((Person)arry[i]).Name);
            }
            arry.Sort();
            Console.WriteLine("排序之后");
            for (int i = 0; i < arry.Count; i++)
            {
                Console.WriteLine(((Person)arry[i]).Name);
            }
            Console.ReadKey();
        }

        public class Person : IComparable//实现IComparable接口，则可以调用排序方法Sort()，否则对于有多个参数的对象，Sort()方法不知道该具体比较哪一项
        {
            public string Name { get; set; }
            public int Age { get; set; }

            
            public int CompareTo(object obj)//返回值>0表示比比较对象大,=0跟比较对象相等,<0比比较对象小
            {
                Person p = obj as Person;//因为传入的是object类型，所以要将传入的参数转换为需要比较的类型
                if (p == null)
                {
                    throw new ArgumentException();//参数无效异常
                }
                else
                {
                    //return this.Age - p.Age;//可以自定义按照类型的某一属性进行比较
                    return this.Name.Length - p.Name.Length;
                }
            }
        }
    }
}

实现IComparable接口，则ArrayList可以调用排序方法Sort()，否则对于有多个参数的对象，Sort()方法不知道该具体比较哪一项

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

namespace UseOfICompare
{
    class Program
    {
        static void Main(string[] args)
        {
            ArrayList array = new ArrayList() {new Person(){Name = "Alice",Age = 42},new Person(){Name = "dog",Age = 62},new Person(){Name = "cat",Age = 15}};
            Console.WriteLine("比较前");
            for (int i = 0; i < array.Count; i++)
            {
                Console.WriteLine(((Person)array[i]).Name);
            }

            //array.Sort(new CompareByNameLength());
            array.Sort(new CompareByAge());

            Console.WriteLine("比较之后");
            for (int i = 0; i < array.Count; i++)
            {
                Console.WriteLine(((Person)array[i]).Name);
            }
            Console.ReadKey();
        }
    }

    public class Person
    {
        public string Name { get; set; }
        public int Age { get; set; }
    }

    public class CompareByNameLength : IComparer//实现IComparer接口，其实是做了一个比较器，比较器专门用来比较某一项，将比较器作为参数传入ArrayList的排序Sort()方法就可以实现比较了
    {
        public int Compare(object x, object y)//同样返回值是>0,<0,=0
        {
            Person p1 = x as Person;
            Person p2 = y as Person;
            if (p1 == null && p2 == null)
            {
                throw new ArgumentException();//参数类型错误异常
            }
            else
            {
                return p1.Name.Length - p2.Name.Length;//按姓名长度比较
            }
        }
    }

    public class CompareByAge : IComparer
    {
        public int Compare(object x, object y)
        {
            Person p1 = x as Person;
            Person p2 = y as Person;
            if (p1 == null && p2 == null)
            {
                throw new ArgumentException();//参数类型错误
            }
            else
            {
                return p1.Age - p2.Age;
            }
        }
    }

}

就一个Person对象来说，如果有两个属性，分别为Name和Age，如果某个时段想用Name长度来作为比较，某个时段想用Age大小来作为比较，如果让Person实现ICompareable接口就不太合适了，因为实现ICompareable接口再调用ArrayList的Sort()方法对按照在比较Person类中定义的规则进行一项的比较。

public int Compare(object x, object y)方法中传入两个对象是内部实现，只需要调用array.sort(new XXXXX());就可以了。