DataView objView = new DataView(FileList);   //FileList是结果集DataTable
objView.Sort = "CreateTime DESC";            //CreateTime是结果集中的列

GridView1.DataSource = objView;
GridView1.DataKeyNames = new string[] { "FileURL" };
GridView1.DataBind();

------解决方案--------------------
前台:
HTML code

//设Grid的OnSorting="GridData_Sorting" 
<asp:TemplateField HeaderText="广告标题" SortExpression="Title">
    <ItemTemplate>
        <%# Eval("Title")%>
    </ItemTemplate>
</asp:TemplateField>