ArrayList排序问题

ArrayList集合，包含默认的方法Sort(),这个方法使用时可以不带参数，此时使用默认的比较方式，也可以给它传送IComparer接口。

给ArrayList填充了简单类型时，例如整数或者字符串，就会进行默认的比较。对于自己的类，必须在类定义中实现IComparable，或创建一个支持IComparer的类，来进行比较。

1.Person.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace ConsoleApplication2

{

public class Person:IComparable

{

    public string Name;

    public int Age;

    public Person(string name, int age)

    {

        Name = name;

        Age = age;

    }

    public int CompareTo(object obj)

    {

        if (obj is Person)

        {

            Person otherPerson = obj as Person;

            return this.Age - otherPerson.Age;

        }

        else {

            throw new ArgumentException("Object to compare to  is not a Person object ");

        }

    }

}

}

2.PsersonCompareName.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Collections;

namespace ConsoleApplication2

{

public class PsersonCompareName:IComparer

{

    public static IComparer Default = new PsersonCompareName();

    public int Compare(object x, object y)

    {

        if (x is Person && y is Person)

        {

            return Comparer.Default.Compare(((Person)x).Name, ((Person)y).Name);

        }

        else {

            throw new ArgumentException("error");

        }

    }

}

}

3.调用

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Collections;

namespace ConsoleApplication2

{

class Program

{

    static void Main(string[] args)

    {

        ArrayList list = new ArrayList();

        list.Add(new Person("R",30));

        list.Add(new Person("D", 25));

        list.Add(new Person("M", 27));

        list.Add(new Person("B", 44));

        Console.WriteLine("Unsorted people:");

        for (int i = 0; i < list.Count; i++)

        {

            Console.WriteLine((list[i] as Person).Name + "  " + (list[i] as Person).Age);

        }

        Console.WriteLine("default sort");

        list.Sort();

        for (int i = 0; i < list.Count; i++)

        {

            Console.WriteLine((list[i] as Person).Name + "  " + (list[i] as Person).Age);

        }

        Console.WriteLine("not default sort");

        list.Sort(PsersonCompareName.Default);

        for (int i = 0; i < list.Count; i++)

        {

            Console.WriteLine((list[i] as Person).Name + "  " + (list[i] as Person).Age);

        }

    }

}

}

2.png