MimeKit.MimeMessage.CreateFromMailMessage C# (CSharp) Method

		public static MimeMessage CreateFromMailMessage (MailMessage message)
		{
			if (message == null)
				throw new ArgumentNullException (nameof (message));

			var headers = new List<Header> ();
			foreach (var field in message.Headers.AllKeys) {
				foreach (var value in message.Headers.GetValues (field))
					headers.Add (new Header (field, value));
			}

			var msg = new MimeMessage (ParserOptions.Default, headers);
			MimeEntity body = null;

			// Note: If the user has already sent their MailMessage via System.Net.Mail.SmtpClient,
			// then the following MailMessage properties will have been merged into the Headers, so
			// check to make sure our MimeMessage properties are empty before adding them.
			if (msg.Sender == null && message.Sender != null)
				msg.Sender = (MailboxAddress) message.Sender;
			if (msg.From.Count == 0 && message.From != null)
				msg.From.Add ((MailboxAddress) message.From);
#if NET_3_5
			if (msg.ReplyTo.Count == 0 && message.ReplyTo != null)
				msg.ReplyTo.Add ((MailboxAddress) message.ReplyTo);
#else
			if (msg.ReplyTo.Count == 0 && message.ReplyToList.Count > 0)
				msg.ReplyTo.AddRange ((InternetAddressList) message.ReplyToList);
#endif
			if (msg.To.Count == 0 && message.To.Count > 0)
				msg.To.AddRange ((InternetAddressList) message.To);
			if (msg.Cc.Count == 0 && message.CC.Count > 0)
				msg.Cc.AddRange ((InternetAddressList) message.CC);
			if (msg.Bcc.Count == 0 && message.Bcc.Count > 0)
				msg.Bcc.AddRange ((InternetAddressList) message.Bcc);
			if (string.IsNullOrEmpty (msg.Subject))
				msg.Subject = message.Subject ?? string.Empty;

			switch (message.Priority) {
			case MailPriority.Normal:
				msg.Headers.RemoveAll (HeaderId.XMSMailPriority);
				msg.Headers.RemoveAll (HeaderId.Importance);
				msg.Headers.RemoveAll (HeaderId.XPriority);
				msg.Headers.RemoveAll (HeaderId.Priority);
				break;
			case MailPriority.High:
				msg.Headers.Replace (HeaderId.Priority, "urgent");
				msg.Headers.Replace (HeaderId.Importance, "high");
				msg.Headers.Replace (HeaderId.XPriority, "2 (High)");
				break;
			case MailPriority.Low:
				msg.Headers.Replace (HeaderId.Priority, "non-urgent");
				msg.Headers.Replace (HeaderId.Importance, "low");
				msg.Headers.Replace (HeaderId.XPriority, "4 (Low)");
				break;
			}

			if (!string.IsNullOrEmpty (message.Body)) {
				var text = new TextPart (message.IsBodyHtml ? "html" : "plain");
				text.SetText (message.BodyEncoding ?? Encoding.UTF8, message.Body);
				body = text;
			}

			if (message.AlternateViews.Count > 0) {
				var alternative = new MultipartAlternative ();

				if (body != null)
					alternative.Add (body);

				foreach (var view in message.AlternateViews) {
					var part = GetMimePart (view);

					if (view.BaseUri != null)
						part.ContentLocation = view.BaseUri;

					if (view.LinkedResources.Count > 0) {
						var type = part.ContentType.MediaType + "/" + part.ContentType.MediaSubtype;
						var related = new MultipartRelated ();

						related.ContentType.Parameters.Add ("type", type);

						if (view.BaseUri != null)
							related.ContentLocation = view.BaseUri;

						related.Add (part);

						foreach (var resource in view.LinkedResources) {
							part = GetMimePart (resource);

							if (resource.ContentLink != null)
								part.ContentLocation = resource.ContentLink;

							related.Add (part);
						}

						alternative.Add (related);
					} else {
						alternative.Add (part);
					}
				}

				body = alternative;
			}

			if (body == null)
				body = new TextPart (message.IsBodyHtml ? "html" : "plain");

			if (message.Attachments.Count > 0) {
				var mixed = new Multipart ("mixed");

				if (body != null)
					mixed.Add (body);

				foreach (var attachment in message.Attachments)
					mixed.Add (GetMimePart (attachment));

				body = mixed;
			}

			msg.Body = body;

			return msg;
		}