Mdi中打开子窗体

private void OpenedFrm(Form FrmCls)
        {
            int i = 0;
            int j = 0;
            for (i = 0; i < MdiChildren.Length; i++)
            {
                if (MdiChildren[i].Name == FrmCls.Name)
                {
                    j++;
                    break;
                }
            }

            if (j == 0)
            {
                FrmCls.MdiParent = this;
                FrmCls.Show();
                FrmCls.WindowState = FormWindowState.Maximized;
            }
            else
            {
                MdiChildren[i].Activate();                
            }
        }