Setting More than 1 DataKeys In GridView

<asp:GridView ID="gvwSiteVisitDetails" runat="server" Width="100%"
AllowPaging="True" DataKeyNames="GATExecutionDepartmentSiteVisitID,GATSiteVisitID"
onrowdatabound="gvwSiteVisitDetails_RowDataBound" onpageindexchanging="gvwSiteVisitDetails_PageIndexChanging"
>
<Columns>
<asp:BoundField HeaderText="GATExecutionDepartmentSiteVisitID" Visible="False" DataField="GATExecutionDepartmentSiteVisitID" />
<asp:BoundField HeaderText="GATSiteVisitID" Visible="False" DataField="GATSiteVisitID" />
</Columns>
<EmptyDataTemplate>
<table border="0" cellpadding="0" cellspacing="0" width="100%">
<tr>
<td style="text-align: center; height: 16px;">
<asp:Label ID="lblSiteVisit" runat="server" Font-Bold="False" SkinID="NoRecords"
Text="No site visit details are loaded" Width="100%"></asp:Label>
</td>
</tr>
</table>
</EmptyDataTemplate>
</asp:GridView>