数组自定义排序：IComparable和IComparer接口

　　首先先说一下IComparable和IComparer的区别，前者必须在实体类中实现，后者可以单独出现在一个排序类中，即此类只包含一个compare方法。

　　Array类使用快速算法对数组中的元素进行排序。sort（）方法需要数组中的元素实现IComparable接口，下例演示了一个自定义的排序：

 class Program

    {

        static void Main(string[] args)

        {

            Person[] persons ={

                              new Person{firstName ="Dsldkjf",lastName="Agjkl"},

                              new Person{firstName ="gpok",lastName="gjys"},

                              new Person{firstName ="ugkdf",lastName="Agjkl"},

                              new Person{firstName ="idfkd",lastName="6dfbh"}

                              };



            foreach (var p in persons)

            {

                Console.WriteLine(p);

            }

            Console.WriteLine("---------------------------------------------");

            Array.Sort(persons);

            foreach (var p in persons)

            {

                Console.WriteLine(p);

            }

            Console.ReadKey();

        }

    }



    class Person : IComparable<Person>

    {

        public string firstName=string.Empty;

        public string lastName = string.Empty;



        public int CompareTo(Person other)

        {

            if (other == null) return 1;

            int result = string.Compare(this.lastName, other.lastName);

            if (result == 0)

            {

                result = string.Compare(this.firstName, other.firstName);

            }

            return result;

        }



        public override string ToString()

        {

            return string.Format("{0} {1}" ,firstName,lastName);

        }

    }

结果：

下面实现一个带选择功能的排序：

class Program

    {

        static void Main(string[] args)

        {

            Person[] persons ={

                              new Person{firstName ="Dsldkjf",lastName="Agjkl"},

                              new Person{firstName ="gpok",lastName="gjys"},

                              new Person{firstName ="ugkdf",lastName="Agjkl"},

                              new Person{firstName ="idfkd",lastName="6dfbh"}

                              };



            foreach (var p in persons)

            {

                Console.WriteLine(p);

            }

            Console.WriteLine("---------------------------------------------");

            Array.Sort(persons,new PersonComparer(PersonComparType.lastName));

            foreach (var p in persons)

            {

                Console.WriteLine(p);

            }

            Console.ReadKey();

        }

    }



    public struct Person

    {

        public string firstName;

        public string lastName;



        public override string ToString()

        {

            return string.Format("{0} {1}", firstName, lastName);

        }

    }

    public enum PersonComparType

    {

        firstName,

        lastName

    }



    public class PersonComparer : IComparer<Person>

    {

        private PersonComparType type;

        public PersonComparer(PersonComparType type)

        {

            this.type = type;

        }

        public int Compare(Person x, Person y)

        {

            //假如Person是一个类的话 需要进行下面判断

            //if (x ==null && y == null) return 0;

            //if (x == null) return 1;

            //if (y == null) return -1;

            switch (type)

            { 

                case PersonComparType.firstName:

                    return string.Compare(x.firstName, y.firstName);

                case PersonComparType.lastName:

                    return string.Compare(x.lastName, y.lastName);

                default:

                    throw new ArgumentException("unexpected compare type");

            }

 

        }

    }

结果：