怎么判断动态生成的button是否被点击

如何判断动态生成的button是否被点击
我在前台页面用Repeater控件动态生成了Button按钮，现在不知怎么判断用户点击的是那个按钮？
protected void btndownload_Click(object sender, EventArgs e) 
  {
  foreach (RepeaterItem ri in this.Repeater2.Items)
  {
  Button btn = ri.FindControl("lbndown") as Button;
   
  if ()//各位大侠，我想问问这个判断条件应该怎么来写
  {
  HiddenField hfId = ri.FindControl("HiddenFieldId") as HiddenField;
  if (hfId != null)
  {
  string idstr = hfId.Value;
  int id = int.Parse(idstr);
  checkpwdById(id);
  break;
  }
  }

  }
}

------解决方案--------------------------------------------------------
Button s = sender as Button;
s就是点击的那个