设计模式代码示例

单例模式（线程）
 using System;
using System.Collections;
using System.Threading;
//
//
//  Generated by StarUML(tm) C# Add-In
//
//  @ Project : 设计模式
//  @ File Name : LoadBalancer.cs
//  @ Date : 2010/12/21
//  @ Author : 
//
//


namespace LoadBalancer{
    public class LoadBalancer {
        private static LoadBalancer balancer ;
        private ArrayList servers = new ArrayList() ;

        private Random random = new Random();

        protected LoadBalancer()
        {
            servers.Add("Server1");
            servers.Add("Server2");
            servers.Add("Server3");
            servers.Add("server4");
            servers.Add("server5");
        }



        public static LoadBalancer GetLoadBalancer()
        {
            if ( balancer == null)
            {
                Mutex mutex = new Mutex();
                mutex.WaitOne();
                if (balancer == null)
                {
                    balancer = new LoadBalancer();
                  
                }
                mutex.Close();
            }
            return balancer;
        }

        public string Server
        {
            get
            {
                int r = random.Next(servers.Count);
                return servers[r].ToString();
            }
        }
        
    }
}