调用LIST的Sort的时候会调用IComparer的默认实现，quicksort会调用每个元素的CompareTo的IComparable实现

 

using System;using System.Collections.Generic;using System.Linq;using System.Text;namespace ComparerTest{    class Employee : IComparable
    
         {        private int empID;        private int yearOfSvc = 1;        public Employee(int empID)        {            this.empID = empID;        }        public Employee(int empID, int yearOfSvc)        {            this.empID = empID;            this.yearOfSvc = yearOfSvc;        }        public override string ToString()        {            return "ID: " + empID.ToString()                + "  yearOfSvc: " + yearOfSvc.ToString();        }        public bool Equals(Employee other)        {            if (this.empID == other.empID)            {                return true;            }            else            {                return false;            }        }        //获取Comparer对象的静态方法        public static EmployeeComparer GetComparer()        {            return new Employee.EmployeeComparer();        }        //比较委托回Employee        //Employee使用整形的默认        //CompareTo方法        public int CompareTo(Employee rhs)        {            return this.empID.CompareTo(rhs.empID);        }        //自定义Comparer要调用的特殊表现        public int CompareTo(Employee rhs,            Employee.EmployeeComparer.ComparisonType whichComparision)        {            switch (whichComparision)            {                 case Employee.EmployeeComparer.ComparisonType.EmpID:                    return this.empID.CompareTo(rhs.empID);                case Employee.EmployeeComparer.ComparisonType.Yrs:                    return this.yearOfSvc.CompareTo(rhs.yearOfSvc);            }            return 0;        }        //实现IComparer的内嵌类        public class EmployeeComparer : IComparer
     
              {            private Employee.EmployeeComparer.ComparisonType whichComparision;            public enum ComparisonType            {                EmpID,                Yrs            };            public bool Equals(Employee lhs, Employee rhs)            {                return this.Compare(lhs, rhs) == 0;            }            //让Empolyee对象自己比较            public int Compare(Employee lhs, Employee rhs)            {                return lhs.CompareTo(rhs, WhichComparison);            }            public int GetHashCode(Employee e)            {                return e.GetHashCode();            }            public Employee.EmployeeComparer.ComparisonType WhichComparison            {                set                {                    whichComparision = value;                }                get                 {                    return whichComparision;                }            }        }    }    class Program    {        static void Main(string[] args)        {            List
      
        empArray = new List
       
        ();            Random ra = new Random();            for (int i = 0; i < 5; i++)            {                empArray.Add(new Employee(ra.Next(10)+100,ra.Next(20)));            }            for (int i = 0; i < empArray.Count; i++)            {                Console.Write("\n{0}",empArray[i].ToString());            }            Console.WriteLine();            Console.WriteLine();            Employee.EmployeeComparer c =  Employee.GetComparer();            c.WhichComparison = Employee.EmployeeComparer.ComparisonType.EmpID;            empArray.Sort(c);            for (int i = 0; i < empArray.Count; i++)            {                Console.Write("\n{0}", empArray[i].ToString());            }            Console.WriteLine();            Console.WriteLine();            Employee.EmployeeComparer c2 = Employee.GetComparer();            c.WhichComparison = Employee.EmployeeComparer.ComparisonType.Yrs;            empArray.Sort(c2);            for (int i = 0; i < empArray.Count; i++)            {                Console.Write("\n{0}", empArray[i].ToString());            }            Console.ReadLine();        }    }}