利用单例模式解决WinForm中子窗体只允许打开一次的问题

子窗体部分代码：

private static ZiChuangTi instance = null;        public static ZiChuangTi Getinstance        {get            {                if (instance == null)                {                     instance=new ZiChuangTi();                }                return instance;            }        }public ZiChuangTi()        {                instance=this ;        }

主窗体部分代码：

 

ZiChuangTi zct= ZiChuangTi.Getinstance;         zct.Show();