父生子窗口

 add_R add_user = new add_R();
            for (int x = 0; x < this.MdiChildren.Length; x++)
            {
                Form tempChild = (Form)this.MdiChildren[x];
                tempChild.Close();
            }
            add_user.MdiParent = this;
            add_user.Tag = this.loginlb.Text.Trim();
            add_user.WindowState = FormWindowState.Maximized;
            add_user.Show();