WndProc

        protected override void WndProc(ref Message m)
        {
  
            //拦截窗体最小化按钮消息 
            if (m.Msg == 0x0112)
            {
                if (m.WParam.ToInt32() == 0xF020)
                {
                    this.Visible = true; 
                    return;
                }
            }
            base.WndProc(ref m);
        }