private void ToSingleFile(object sender, RoutedEventArgs e)
        {
            var dlg = new SaveFileDialog
            {
                FileName   = "exports",
                DefaultExt = "rtf",
                Filter     = "Rich Text Files|*.rtf"
            };

            if (dlg.ShowDialog(this) != true)
            {
                return;
            }

            var document = new FlowDocument();


            foreach (var source in TextFileItems.Where(elem => elem.IsChecked && !elem.IsFolder))
            {
                var file = TextFile.Load(source.Filename);
                if (file == null)
                {
                    continue;
                }

                document = document.AddFlowDocument(file.Document);
            }

            //TextFile.SaveFile(dlg.FileName,document);

            var blubb = XamlWriter.Save(document);

            System.Diagnostics.Debug.WriteLine(blubb);
            var test = ConvertXamlToRtf(blubb);

            File.AppendAllText(dlg.FileName, test);
        }