在ios文档选择器中通过.docx进行筛选

要向UIDocumentMenuViewController提供什么统一类型标识以允许用户选择*.docx文件？

系统声明的统一类型标识符中的文档没有列出允许按.docx进行筛选的公共UTType。标准*.doc文件存在标识符，但不存在*.docx，是否存在替代UTType？

这是我当前的代码：

var allowedDocumentTypes = new string[] {
    UTType.RTF,
    UTType.Text,
    UTType.PDF,
    UTType.UTF8PlainText,
    UTType.RTFD,
    UTType.UTF16ExternalPlainText,
    UTType.UTF16PlainText,
    UTType.UTF8PlainText,
    UTType.FlatRTFD,
    "com.microsoft.word.doc",
    "com.microsoft.word.docx" // An attempt to include docx filtering.
};
var pickerMenu = new UIDocumentMenuViewController(allowedDocumentTypes, UIDocumentPickerMode.Open);
pickerMenu.DidPickDocumentPicker += (sender, args) =>
{
    args.DocumentPicker.DidPickDocument += (sndr, pArgs) =>
    {
        var securityEnabled = pArgs.Url.StartAccessingSecurityScopedResource();
        FileInfo fi = new FileInfo(pArgs.Url.Path);
        var result = new SelectFileResult();
        result.FilePath = fi.FullName;
        result.FileName = fi.Name;
        NSUrlRequest urlReq = NSUrlRequest.FromUrl(pArgs.Url);
        NSUrlResponse response;
        NSError error;;
        var data = NSUrlConnection.SendSynchronousRequest(urlReq, out response, out error);
        result.MimeType = response.MimeType;
        Action onFileConsumeDone = () =>
        {
            pArgs.Url.StopAccessingSecurityScopedResource();
        };
        onFileSelected(result, onFileConsumeDone);
    };
    // Display the document picker
    AppDelegate.TopViewController.PresentViewController(args.DocumentPicker, true, null);
};
pickerMenu.ModalPresentationStyle = UIModalPresentationStyle.Popover;
AppDelegate.TopViewController.PresentViewController(pickerMenu, true, null);

我在黑暗中拍摄了一张照片，并包含了标识符com.microsoft.word.docx，但它不会触发docx的过滤。

我目前的解决方案是C#，但接受了objective-C和swift解决方案。