private void AddFiles(object obj) { var supportedFormatsString = new StringBuilder(); for (var index = 0; index < _supportedFormats.LoadedPlugins.Count; index++) { var file = _supportedFormats.LoadedPlugins[index]; supportedFormatsString.Append($"*{file.Plugin.FileExtension}"); if (index != _supportedFormats.LoadedPlugins.Count - 1) { supportedFormatsString.Append(";"); } } var filter = $"Supported Formats ({supportedFormatsString})|{supportedFormatsString}"; var openFileDialog = new VistaOpenFileDialog { Filter = filter }; if (openFileDialog.ShowDialog() != true) { return; } var files = openFileDialog.FileNames; _importer.AddBooks(files); }