winform渐变窗口显示/关闭

  //渐渐的消失
    for (int iNum = 10; iNum >= 0; iNum --)
     {
        //变更窗体的不透明度
        this.Opacity = 0.1 * iNum;
        //暂停
         System.Threading.Thread.Sleep(100);
     }

     //渐渐的显示
    for (int iNum = 0; iNum <= 10; iNum ++)
     {
         //变更窗体的不透明度
        this.Opacity = 0.1 * iNum;
        //暂停
         System.Threading.Thread.Sleep(100);
     }