将PDF从Cloudinary转换为邮件附件将MemoryStream转换为Stream

Cloudinary System.Net.Mail Attachment :

 private static Attachment CreateAttachementFromMessage(Stream stream)
        {
            var memoryStream = new MemoryStream();
            stream.CopyTo(memoryStream);

            return new Attachment(
                memoryStream,
                "Anhang zur Bestellung",
                "application/pdf"
                );
        }

var stream = getFileStream(resourceId);
private getFileStream(resourceId){

                var imageData=_cloudinary.GetResource(resourceId);

                if (imageData.StatusCode != HttpStatusCode.OK)
                {
                    return null;
                }

                var downloadUrl = _cloudinary.Api.UrlImgUp.Secure().BuildUrl(resourceId);

                if (string.IsNullOrEmpty(downloadUrl))
                {
                    return null;
                }

                return DownloadStream(new Uri(downloadUrl));}


}

流不是空的,但邮件内容本身似乎无效。

有什么想法吗?创建流、转换流或创建附件是否有问题?

https://i.stack.imgur.com/IveNn.png

编辑2:实际附件内容:

https://i.stack.imgur.com/x85AO.png