private void BrowseBtn_Click(object sender, RoutedEventArgs e) { var fileDialogObject = new Microsoft.Win32.OpenFileDialog(); var fullPathList = fileDialogObject.BrowseMultipleFilesToOpen("Audio Files|*.wav").ToList(); fullPathList.ForEach(file => { if (_mediapoolFilesWithFullPath.Contains(file) == false) { _mediapoolFilesWithFullPath.Add(file); } }); var fileNameList = fileDialogObject.SafeFileNames.ToList(); if (fileNameList?.Count > 0) { fileNameList.ToList().ForEach(file => { if (!MediaPool.Items.Contains(file)) { MediaPool.Items.Add(file); } }); } }