你可能想繼續使用的MailBee ......但如果你是開放的選擇，讓我，如果你用我的開源MimeKit回答這個問題/ MailKit庫代替：
當MimeKit的MIME解析器遇到了Content-Type頭匹配application/vnd.ms-tnef或application/ms-tnef，它會自動使用專用TnefPart類來表示連接附件換貨。
要從中提取封裝的附件，您可以簡單地使用 ExtractAttachments()方法，該方法可能與MailBee的GetAttachmentsFromTnef()方法非常相似。
你的代碼的MailBee到MimeKit的翻譯應該是這樣的：
var attachments = message.Attachments.ToList();
var encapsulated = attachments.OfType<TnefPart>().SelectMany(a => a.ExtractAttachments());
// Add encapsulated attachments
attachments.AddRange(encapsulated);
最有可能的MailBee的IsTnef屬性返回給你假的原因，然而，可能是因爲Content-Type頭不匹配我前面提到的tnef mime-types。如果確實如此，那麼我在上面發佈的翻譯代碼也會在MimeKit下失敗。
但是......
MimeKit還規定，如果你決定使用另一種方法來確定一個MIME部分包含TNEF內容，您可以使用較低級別的TNEF支持類。
static void ExtractAttachments (MimePart attachment, IList<MimeEntity> attachments)
{
using (var reader = new TnefReader (attachment.ContentObject.Open(), 0, TnefComplianceMode.Loose)) {
// skip past the non-attachment tnef content...
while (reader.ReadNextAttribute()) {
if (reader.AttributeLevel == TnefAttributeLevel.Attachment)
break;
}
if (reader.AttributeLevel == TnefAttributeLevel.Attachment)
ExtractAttachments (reader, attachments);
}
}
static void ExtractAttachments (TnefReader reader, IList<MimeEntity> attachments)
{
var attachMethod = TnefAttachMethod.ByValue;
var filter = new BestEncodingFilter();
var prop = reader.TnefPropertyReader;
MimePart attachment = null;
int outIndex, outLength;
TnefAttachFlags flags;
string[] mimeType;
byte[] attachData;
string text;
do {
if (reader.AttributeLevel != TnefAttributeLevel.Attachment)
break;
switch (reader.AttributeTag) {
case TnefAttributeTag.AttachRenderData:
attachMethod = TnefAttachMethod.ByValue;
attachment = new MimePart();
break;
case TnefAttributeTag.Attachment:
if (attachment == null)
break;
while (prop.ReadNextProperty()) {
switch (prop.PropertyTag.Id) {
case TnefPropertyId.AttachLongFilename:
attachment.FileName = prop.ReadValueAsString();
break;
case TnefPropertyId.AttachFilename:
if (attachment.FileName == null)
attachment.FileName = prop.ReadValueAsString();
break;
case TnefPropertyId.AttachContentLocation:
text = prop.ReadValueAsString();
if (Uri.IsWellFormedUriString (text, UriKind.Absolute))
attachment.ContentLocation = new Uri (text, UriKind.Absolute);
else if (Uri.IsWellFormedUriString (text, UriKind.Relative))
attachment.ContentLocation = new Uri (text, UriKind.Relative);
break;
case TnefPropertyId.AttachContentBase:
text = prop.ReadValueAsString();
attachment.ContentBase = new Uri (text, UriKind.Absolute);
break;
case TnefPropertyId.AttachContentId:
attachment.ContentId = prop.ReadValueAsString();
break;
case TnefPropertyId.AttachDisposition:
text = prop.ReadValueAsString();
if (attachment.ContentDisposition == null)
attachment.ContentDisposition = new ContentDisposition (text);
else
attachment.ContentDisposition.Disposition = text;
break;
case TnefPropertyId.AttachData:
var stream = prop.GetRawValueReadStream();
var content = new MemoryStream();
var guid = new byte[16];
if (attachMethod == TnefAttachMethod.EmbeddedMessage) {
var tnef = new TnefPart();
foreach (var param in attachment.ContentType.Parameters)
tnef.ContentType.Parameters[param.Name] = param.Value;
if (attachment.ContentDisposition != null)
tnef.ContentDisposition = attachment.ContentDisposition;
attachment = tnef;
}
// read the GUID
stream.Read (guid, 0, 16);
// the rest is content
using (var filtered = new FilteredStream (content)) {
filtered.Add (filter);
stream.CopyTo (filtered, 4096);
filtered.Flush();
}
content.Position = 0;
attachment.ContentTransferEncoding = filter.GetBestEncoding (EncodingConstraint.SevenBit);
attachment.ContentObject = new ContentObject (content);
filter.Reset();
attachments.Add (attachment);
break;
case TnefPropertyId.AttachMethod:
attachMethod = (TnefAttachMethod) prop.ReadValueAsInt32();
break;
case TnefPropertyId.AttachMimeTag:
mimeType = prop.ReadValueAsString().Split ('/');
if (mimeType.Length == 2) {
attachment.ContentType.MediaType = mimeType[0].Trim();
attachment.ContentType.MediaSubtype = mimeType[1].Trim();
}
break;
case TnefPropertyId.AttachFlags:
flags = (TnefAttachFlags) prop.ReadValueAsInt32();
if ((flags & TnefAttachFlags.RenderedInBody) != 0) {
if (attachment.ContentDisposition == null)
attachment.ContentDisposition = new ContentDisposition (ContentDisposition.Inline);
else
attachment.ContentDisposition.Disposition = ContentDisposition.Inline;
}
break;
case TnefPropertyId.AttachSize:
if (attachment.ContentDisposition == null)
attachment.ContentDisposition = new ContentDisposition();
attachment.ContentDisposition.Size = prop.ReadValueAsInt64();
break;
case TnefPropertyId.DisplayName:
attachment.ContentType.Name = prop.ReadValueAsString();
break;
}
}
break;
case TnefAttributeTag.AttachCreateDate:
if (attachment != null) {
if (attachment.ContentDisposition == null)
attachment.ContentDisposition = new ContentDisposition();
attachment.ContentDisposition.CreationDate = prop.ReadValueAsDateTime();
}
break;
case TnefAttributeTag.AttachModifyDate:
if (attachment != null) {
if (attachment.ContentDisposition == null)
attachment.ContentDisposition = new ContentDisposition();
attachment.ContentDisposition.ModificationDate = prop.ReadValueAsDateTime();
}
break;
case TnefAttributeTag.AttachTitle:
if (attachment != null && string.IsNullOrEmpty (attachment.FileName))
attachment.FileName = prop.ReadValueAsString();
break;
case TnefAttributeTag.AttachMetaFile:
if (attachment == null)
break;
// TODO: what to do with the meta data?
break;
case TnefAttributeTag.AttachData:
if (attachment == null || attachMethod != TnefAttachMethod.ByValue)
break;
attachData = prop.ReadValueAsBytes();
filter.Flush (attachData, 0, attachData.Length, out outIndex, out outLength);
attachment.ContentTransferEncoding = filter.GetBestEncoding (EncodingConstraint.EightBit);
attachment.ContentObject = new ContentObject (new MemoryStream (attachData, false));
filter.Reset();
attachments.Add (attachment);
break;
}
} while (reader.ReadNextAttribute());
}
當然......你也可以只通過這樣騙：
var tnef = new TnefPart { ContentObject = attachment.ContentObject };
attachments.AddRange (tnef.ExtractAttachments());
所以，最終的結果可能是這樣的（如果你決定來匹配文件名代替）：
var attachments = message.Attachments.ToList();
var encapsulated = attachments.OfType<MimePart>()
.Where(x => (x is TnefPart) || x.FileName == "winmail.dat")
.SelectMany(x => {
var tnef = (x as TnefPart) ?? new TnefPart { ContentObject = x.ContentObject };
return tnef.ExtractAttachments();
});
// Add encapsulated attachments
attachments.AddRange(encapsulated);