using asprise_imaging_api;

Result result = new AspriseImaging().Scan(new Request()
    .SetTwainCap(TwainConstants.ICAP_PIXELTYPE, TwainConstants.TWPT_RGB)
    .SetTwainCap(TwainConstants.ICAP_SUPPORTEDSIZES, TwainConstants.TWSS_USLETTER)
    .SetPromptScanMore(true) // prompt to scan more pages
    .AddOutputItem(new RequestOutputItem(AspriseImaging.OUTPUT_SAVE, AspriseImaging.FORMAT_PDF)
      .SetSavePath("U:\${TMS}${EXT}")), // Environment variables in path will be expanded
  "select", true, true); // "select" prompts device selection dialog.

List<string> files = result == null ? null : result.GetImageFiles();
Console.WriteLine("Scanned: " + string.Join(", ", files == null ? new string[0] : files.ToArray()));

Install-Package asprise-scan-scanner-twain-wia-api