if your column is autogenearted then use
Gridview1.column[index].visible=false;
Otherwise set visible false on aspx page
<asp:gridview id="Grid_Show" runat="server" >
<columns>
<asp:templatefield visible="false">
<itemtemplate>
<asp:label id="lblID" runat="server" text="<%#Bind("ID")%>"></asp:label>
</itemtemplate>
</asp:templatefield>
</columns>
</asp:gridview>