foreach(Control ctl in Controls)   
  {   
  if(ctl is Button) //or if(ctl.GetType()==(new Button()).GetType)   
  ..   
  //其它类似      
  }

------解决方案--------------------
考虑容器控件．　若button在容器里．

C# code
private void seachbutton(Control.ControlCollection controls)
        {
            foreach (Control c in controls)
            {
                if (c is Button)
                    ｛　．．．．．｝
                else
                    if (c.Controls.Count > 0)
                        seachbutton(c.Controls);
            }

        }