If you want to use label in grid view you can't use button field you have to use item template in grid view like this:
<Columns>
<asp:TemplateField HeaderText="Label" ItemStyle-Width="50px">
<ItemTemplate>
<asp:Label ID="lbl" runat="server" Text="Your Text" ></asp:Label>
</ItemTemplate>
</asp:TemplateField>
</Columns>
Accept as answer and vote if solve your problem.