checkbox 全选

      <asp:Repeater ID="GridView1" runat="server">
                            <HeaderTemplate>
                             <tr>
   <th scope="col">
                                     <input id="all" type="checkbox" name="all" onclick="check_all(this,'checkid');" />
                                 </th><th scope="col">订单号</th><th scope="col">下单日期</th><th scope="col">订单详情</th><th scope="col">销售等级</th><th scope="col">订单状态</th><th scope="col">&nbsp;</th>
  </tr>
                            </HeaderTemplate>
                            <ItemTemplate>
                              <tr>
   <td>
   <input id="checkbox" runat="server" type="checkbox" value="" />

<script type="text/javascript">
 function check_all(obj,cName)
{
//    var checkboxs = document.getElementsByName(cName);
//   
//    for(var i=0;i<checkboxs.length;i++){checkboxs[i].checked = obj.checked;}
//   
     var check=document.getElementsByTagName("input");
     var allbl;
     var k=0;
   for(var i=0;i<check.length;i++)
   {
      if(check[i].type=="checkbox")
      {
         if(k==0)
         {
           k++;
           allbl=check[i].checked;
         }

          check[i].checked=allbl;
      }
   }
   
}
</script>