之前回答於
http://forums.microsoft.com/msdn-cht/ShowPost.aspx?PostID=765725&SiteID=14

void ClearTextBoxes()
{
foreach(object ctrl in Page.Controls)
{
 if (ctrl is System.Web.UI.HtmlControls.HtmlForm)
 {
  System.Web.UI.HtmlControls.HtmlForm form = (System.Web.UI.HtmlControls.HtmlForm)ctrl;
  foreach(object subctrl in form.Controls)
  {
   if (subctrl is System.Web.UI.WebControls.TextBox)
   {
    TextBox textctrl = (TextBox)subctrl;
    textctrl.Text = "";
   }
  }
 }
}

//特別要注意的是 Html 裡面不要設定到 runat="server" 這樣的會尋找範圍
就要在 System.Web.UI.WebControls.Table 下
剛好今天COPY另一個Html table  過來沒有注意到多弄了這段。

 <table background="ballot_bk1.GIF" border="0" runat="server"
            cellpadding="0" cellspacing="0" style="width: 500px; height: 600px">