c# singleton 的一種實現.

public class Singleton
 {
  private static bool instance_flag=false;
  private Singleton()//將singleton函數變爲private,防止直接調用new來創建它.
  {
   Console.WriteLine("你只可以看到我一次哦");
  }
  public static Singleton GetInstance()
  {
   if (!instance_flag)
   {
    instance_flag=true;
    return new Singleton();
   }
   else return null;
  }
 }
}