Silverlight数据网格-将选定的项目导出到Excel

我在Silverlight中有一个数据网格，它有一个checkboxcolumn绑定到一个属性。

<sdk:DataGridCheckBoxColumn x:Name="chkboxSelect" CanUserReorder="False" CanUserResize="False" 
  Binding="{Binding CopyToForecast}" />

我也有一个导出excel从数据网格看起来像这样。

  public static void ExportDataGrid(DataGrid dGrid)
    {
        SaveFileDialog objSFD = new SaveFileDialog() { DefaultExt = "csv", Filter = "CSV Files (*.csv)|*.csv|Excel XML (*.xml)|*.xml|All files (*.*)|*.*", FilterIndex = 1 };
        if (objSFD.ShowDialog() == true)
        {
            string strFormat = objSFD.SafeFileName.Substring(objSFD.SafeFileName.IndexOf('.') + 1).ToUpper();
            StringBuilder strBuilder = new StringBuilder();
            if (dGrid.ItemsSource == null) return;
            List<string> lstFields = new List<string>();
            if (dGrid.HeadersVisibility == DataGridHeadersVisibility.Column || dGrid.HeadersVisibility == DataGridHeadersVisibility.All)
            {
                foreach (DataGridColumn dgcol in dGrid.Columns)
                    lstFields.Add(FormatField(dgcol.Header.ToString(), strFormat));
                BuildStringOfRow(strBuilder, lstFields, strFormat);
            }
            foreach (object data in dGrid.ItemsSource)
            {
                lstFields.Clear();
                foreach (DataGridColumn col in dGrid.Columns)
                {
                    string strValue = "";
                    Binding objBinding = null;
                    if (col is DataGridBoundColumn)
                        objBinding = (col as DataGridBoundColumn).Binding;
                    if (col is DataGridTemplateColumn)
                    {
                        //This is a template column... let us see the underlying dependency object
                        DependencyObject objDO = (col as DataGridTemplateColumn).CellTemplate.LoadContent();
                        FrameworkElement oFE = (FrameworkElement)objDO;
                        FieldInfo oFI = oFE.GetType().GetField("TextProperty");
                        if (oFI != null)
                        {
                            if (oFI.GetValue(null) != null)
                            {
                                if (oFE.GetBindingExpression((DependencyProperty)oFI.GetValue(null)) != null)
                                    objBinding = oFE.GetBindingExpression((DependencyProperty)oFI.GetValue(null)).ParentBinding;
                            }
                        }
                    }
                    if (objBinding != null)
                    {
                        if (objBinding.Path.Path != "")
                        {
                            PropertyInfo pi = data.GetType().GetProperty(objBinding.Path.Path);
                            if (pi != null) strValue = pi.GetValue(data, null).ToString();
                        }
                        if (objBinding.Converter != null)
                        {
                            if (strValue != "")
                                strValue = objBinding.Converter.Convert(strValue, typeof(string), objBinding.ConverterParameter, objBinding.ConverterCulture).ToString();
                            else
                                strValue = objBinding.Converter.Convert(data, typeof(string), objBinding.ConverterParameter, objBinding.ConverterCulture).ToString();
                        }
                    }
                    lstFields.Add(FormatField(strValue, strFormat));
                }
                BuildStringOfRow(strBuilder, lstFields, strFormat);
            }
            StreamWriter sw = new StreamWriter(objSFD.OpenFile());
            if (strFormat == "XML")
            {
                //Let us write the headers for the Excel XML
                                }
            sw.Write(strBuilder.ToString());
            if (strFormat == "XML")
            {
                sw.WriteLine("</Table>");
                sw.WriteLine("</Worksheet>");
                sw.WriteLine("</Workbook>");
            }
            sw.Close();
        }
    }

如何仅从数据网格导出选定(选中)行到excel?