单例模式的两种实现方式

 //第一种实现方式  
 public  class  Singleton
  { 
      private static Singleton Instance;
      
      private Singleton(){}
      
      public static Singleton GetInstance()
      {
          if(Instance==null)
            {
               Instance=new SingLeton();
               return Instance;
             }                      
                return Instance;  
       }

   }

 //第二种实现方式
  public   class    Singleton
  {
      private static Singleton Instance;
        
      private static readonly object locker= new object(); 
      
      private Singleton(){}
 
      public static Singleton GetInstance()
      {
          lock(locker)
          {
            if(Instance==null)
             {
                  Instance=new Singleton();
                  return Instance;
              }
            }
          return Instance;
       }