kindly put a hidden field in your page and fill the value on linkbutton clicked and check this at server side as you want.
<asp:TemplateField ItemStyle-CssClass="font_grid">
<ItemTemplate>
<asp:Button ID="btnEdit" runat="server" CommandArgument='<%#Eval("coRefnr") %>' CommandName="Edit" OnCommand="btnEdit_Command" CssClass='<%#Container.DataItemIndex==0?"displayblock":"displaynone" %>' Text="Edit" />
</ItemTemplate>
</asp:TemplateField>
after getting on server side ,remove the hiddenfield value.