.net Winform 控制子窗体在父窗体出现一次

        private void button1_Click(object sender, EventArgs e)        {            System.Windows.Forms.Form[] mdiForm = this.MdiChildren; //获取窗体的数组            bool openFlage = false;//标识窗体是否打开（true:已打开了一个窗体）            foreach (Form fr in mdiForm) //遍历所有MDIForm窗体            {                if (fr.Name == "SystemSet")//已打开一个窗体则激活并显示出来                {                    fr.Activate(); //激活窗体                    openFlage = true;                    break;                }            }            if (!openFlage)//没有打开窗体则新建并显示出来            {                SystemSet SS = new SystemSet();                SS.StartPosition = FormStartPosition.Manual;                SS.Location = new Point(400, 100);                SS.MdiParent = this;                SS.Show();            }        }

===============lable 控件设置颜色========================

 label2.ForeColor = System.Drawing.Color.Blue;