bind gridview in Page_Load

Hi. I noticed all your examples are binding the gridview within the Page_Load by using RegisterAsyncTask.
is this a better way that defining async select method for each gridview?
`        <asp:GridView ID="GridView1" SelectMethod="GridView1_GetData" runat="server"></asp:GridView>
`
and in code behind:
`        public async Task<IQueryable> GridView1_GetData()`
