主窗体嵌套子窗体方法，可直接引用

/// <summary>

 /// 在主窗体中嵌套子窗体，主窗体中的 IsMdicontainer 设置成True;
        /// </summary>
        /// <param name="p">Panael</param>
        /// <param name="F">子窗体</param>

 private  void AddForm(Panel p, Form F)
        {
            foreach (Control item in p.Controls)
            {
                if (item is Form)
                {
                    ((Form)item).Close();
                }
            }          
            F.MdiParent = this;
            F.Parent = p;
            F.FormBorderStyle = FormBorderStyle.None;
            F.Show();
        }