class Form1
{
  //拖入button的时候把它弄成public的。
  public static event EventHandler OnButtonClick=null;
  void ButtonClick(object sender,EventArgs e)
{
   if(OnButtonClick!=null)
   { 
     OnButtonClick(sender,e);
    }
}
}
class Form2
{
  public Form2()
   {
     Form1.OnButtonClick+=new EventHander(ButtonMinClice);
    }
  void ButtonMinClice(object sender,EventAtgs e)
  {
   this.WindowState = FormWindowState.Minimized;
  }
}