const int WM_SYSCOMMAND = 0x112;
const int SC_CLOSE = 0xF060;
const int SC_MINIMIZE = 0xF020;
const int SC_MAXIMIZE = 0xF030;
protected override void WndProc(ref Message m)
{
  if (m.Msg == WM_SYSCOMMAND)
  {
    if (m.WParam.ToInt32() == SC_MINIMIZE) //是否点击最小化
    {
      //这里写操作代码
      this.Visible = false; //隐藏窗体
      return;
    }
    if (m.WParam.ToInt32() == SC_MAXIMIZE ) //是否点击最大化
    {
       //.....................
    }
    if (m.WParam.ToInt32() == SC_CLOSE ) //是否点击关闭
    {  //.....................}

  }
  base.WndProc(ref m);
}