We have a webgrid view using the setting below:

        <ISWebGrid:WebGrid ID="WebGrid1" runat="server" Height="500px" UseDefaultStyle="True" Width="1000px" OnExport="WebGrid1_Export"
                 DefaultStyleMode="Elegant" DataCacheStorage="Session"
                 OnInitializeDataSource ="WebGrid1_InitializeDataSource" OnPrepareDataBinding="WebGrid1_PrepareDataBinding" OnCustomAggregate="WebGrid1_CustomAggregate">
                 <LayoutSettings PagingMode="VirtualLoad" VirtualLoadMode="LargeData"
                    AllowExport="Yes" PagingExportMode="ExportAllData"
                    AllowFilter="Yes" AllowSorting="Yes" ColumnFooters="Yes">
                </LayoutSettings>

 And we use server side data binding instead of client side binding at the desginer. However when we try to export the data after we do filter, the part which is underlined returns null value and the system crashes. 

protected void WebGrid1_Export(object sender, ISNet.WebUI.WebGrid.ExportEventArgs e)

        {
            e.Table.Rows.Clear();

            DataRowCollection rows = (WebGrid1.DataSourceManager.CurrentDataSource as System.Data.DataView).ToTable().Rows;

            foreach (DataRow row in rows)
            {
                var wgRow = e.Table.CreateRow();

                foreach (WebGridColumn col in e.Table.Columns)
                {
                    if (!col.IsRowChecker)
                    {
                        wgRow.Cells.GetNamedItem(col.Name).Value = row[col.DataMember];
                        wgRow.Cells.GetNamedItem(col.Name).Text = wgRow.Cells.GetNamedItem(col.Name).Value.ToString();
                    }
                }

                e.Table.Rows.Add(wgRow);
            }
        }