单件模式

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

namespace CountClient
{
    public class CountSigleton
    {
        static CountSigleton uniCounter = null;

        private int totNum = 0;

        private CountSigleton()
        {
            Thread.Sleep(2000); 
        }

        public static  CountSigleton Instance
        {
            get
            {
                if (uniCounter==null)
                {
                    uniCounter=new CountSigleton();
                }

                return uniCounter;
            }             
        }

        public void Add()
        {
            totNum++;
        }

        public int GetCounter()
        {
            return totNum; 

        }
    }
}

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

namespace CountClient
{
    public class CountMutilThread
    {
        public CountMutilThread(){
            
        }

        public static void DoSomeWork()
        {
            string results = "";

            CountSigleton MyCounter = CountSigleton.Instance;


            for (int i = 1; i < 5; i++)
            {
                MyCounter.Add();

                results += "线程";
                results += Thread.CurrentThread.Name.ToString() + "——〉";
                results += "当前的计数：";
                results += MyCounter.GetCounter().ToString();
                results += "\n";
                Console.WriteLine(results);
                results = "";

            }
        }

        public void StartMain()
        {
            Thread thread0 = Thread.CurrentThread;
            thread0.Name = "Thread 0";

            Thread thread1 = new Thread(new ThreadStart(DoSomeWork));
            thread1.Name = "Thread 1"; 

            Thread thread2 =new Thread(new ThreadStart(DoSomeWork));    
            thread2.Name = "Thread 2";    

            Thread thread3 =new Thread(new ThreadStart(DoSomeWork));    
            thread3.Name = "Thread 3"; 
   
            thread1.Start();    
            thread2.Start(); 
            thread3.Start(); 
            
            /**////线程0也只执行和其他线程相同的工作
            DoSomeWork(); 

        }
    }
}

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

namespace CountClient
{
    class Program
    {
        static void Main(string[] args)
        {
            CountMutilThread cmt = new CountMutilThread();

            cmt.StartMain();

            Console.ReadLine();
        }
    }
}

单件模式，例子。

保证一个类仅有一个实例

参考：http://terrylee.cnblogs.com/archive/2005/12/09/293509.html