I got this error and I don't know what's wrong with my code...here it is:
<asp:LinkButton runat="server" ID="lnkbtnPDFPreview" Text="Preview"
CommandArgument='<%# DataBinder.Eval(Container.DataItem,"productID") %>'
CommandName="<%# DataBinder.Eval(Container.DataItem,"documentID") %>">
</asp:LinkButton>