1：定义删除按钮
<asp:Button ID="btnDelete" runat="server" Text="删除" OnClientClick="javascript: return ShowMessage()"
OnClick="btnDelete_OnClick" CommandArgument='<%# Eval("Id") %>' />
2：添加对应的脚本
<script language="javascript" type="text/javascript" >
function ShowMessage() {
return confirm("要删除该项吗？");
}
</script>