GridView footer not working

I want to display a total in the GridView footer - nothing unusual there. I've followed the example on the Microsoft website, but it's not working:

<asp:GridView ID="gvTimeOverview" DataSourceID="sdsTimeOverview" AutoGenerateColumns="false" ShowFooter="true" CssClass="gridview" runat="server"> <Columns> <asp:BoundField DataField="DateTimeAdded" HeaderText="Date" DataFormatString="{0:dd/MM/yyyy}" /> <asp:BoundField DataField="DateTimeAdded" HeaderText="Time" DataFormatString="{0:HH:mm}" /> <asp:BoundField DataField="TimeToAdd" HeaderText="Mins Allocated" /> </Columns> </asp:GridView> 

Code:

protected void gvTimeOverview_RowDataBound(object sender, GridViewRowEventArgs e) { if (e.Row.RowType == DataControlRowType.DataRow) { totalMins += Convert.ToInt32(DataBinder.Eval(e.Row.DataItem, "TimeToAdd")); } else if (e.Row.RowType == DataControlRowType.Footer) { e.Row.Cells[0].Text = "Totals:"; e.Row.Cells[1].Text = totalMins.ToString(); e.Row.ForeColor = Color.Black; } } 

Any idea why?