<asp:datagrid id="mydatagrid1" runat="server" 
backcolor="#eeeeee"
bordercolor="#000000"
allowsorting="true"
cellpadding=1
cellspacing=1
fontsize="2"
BorderWidth=1
pagesize="8" GridLines="both" ShowHeader="false" ItemStyle-BorderStyle="solid"
AutoGenerateColumns="False"
DataKeyField="id" 
font-name="宋体"  
pagerstyle-horizontalalign="right"
OnItemCommand="mydatagrid1_itemcommand" OnDataBinding="mydatagrid1_binding" 
OnItemDataBound="mydatagrid1_itemdatabound" 
>对相同列进行合并,应该写在哪个事件里?