The Singleton of Design Pattern单态模式

1 Singleton Definition 单态模式定义
       The main purpose is to gurantee that the instance of class has only one in the application.  some operations, such as connecting to database, are userful for only single instance.
        单态模式的主要作用是保证类的实例只有一个。在很多操作中，比如数据库连接等，这种单实例是很有用的。
 
2 singleton model单态模型


3 related singleton model codes:相关单态模式代码
namespace singleton
{
    public class singleton{
    private int _counter;
    private static singleton _instance;
    private static object _classLock=typeof(singleton);
    private singleton()
    {
        _counter = 0;
    }
    public static singleton CreateInstance()//global point to service
    {
        lock (_classLock)
        {
            if (_instance == null)
                instance = new singleton();
        }
            return _instance;
      }

    public void Counte()
    {
        lock (_classLock)//exclusive lock
            {
                _counter++;
            }
    }

     public int Counter
    {    
        get
            {
                return _counter;
            }
    }
  }

    class Program
    {
        static void Main(string[] args)
        {
            singleton hiron = singleton.CreateInstance();
            hiron.Counte();
            singleton hrg = singleton.CreateInstance();
            hrg.Counte();
            Console.WriteLine(hrg.Counter);
        }    
    }
}
excution result:
instance hiron and hrg will refer to the same instance actually, and the output is 2