DataGrid paging does not work properly

Hi,
In my website there is a List which I try to print in several pages in DataGrid. The problem is in the paging links (1 2 3 4 ...). The first page of contents is printed properly. But whenever I try to click on the second page of results, there comes an execution error. It appears at
ResGrid.DataBind();
line and it says that CurrentPageIndex should be >=0 and less than PageCount.
Can anyone help me? This is the code i'm talking about

.aspx file

id="lblTracker" runat="server" />

            runat="server"
            ID="ResGrid"
            AllowPaging="true"
            cellpadding=5
            gridlines="Vertical"
            onPageIndexChanged="setPage"
            PageSize="15">



                         position="Bottom"
             Mode="NumericPages"
             horizontalalign="right" />

aspx.cs file

List Results_final = new List();

bindGrid();

protected void bindGrid()
    {
        ResGrid.DataSource = Results_final;
        ResGrid.DataBind();
        lblTracker.Text = "Page " + (ResGrid.CurrentPageIndex + 1) + " of " + ResGrid.PageCount;
    }

protected void setPage(Object src, DataGridPageChangedEventArgs e)
    {
        ResGrid.CurrentPageIndex = e.NewPageIndex;
        bindGrid();
    }