將MailMessage轉換爲Stream刪除密件抄送

Question

使用此SO帖子（Convert MailMessage to Raw text），我們能夠將MailMessage作爲流獲取。但是，Bcc被刪除。 To和CC仍然工作，但不是密件抄送。

爲什麼會被刪除，以及如何保存？

Answer 1

很確定BCC字段永遠不會與消息一起發送。

BCC字段用於向收件人發送「盲碳副本」。從WikiPedia：

在對應的情況下，盲複寫本（縮寫密件:)允許消息隱藏在密件輸入的人的發送者：從所述其它接收者字段。

如果密件抄送字段中的收件人實際上包含在電子郵件的原始SMTP文本中，則該保證無法執行。

您在問題中鏈接到的方法很可能被SmtpClient用於準備傳輸的消息。因此，爲了保持預期的行爲，它將不得不忽略BCC字段。

要真正保持它，你將不得不手動將其插入到輸出文本：

var email = new MailMessage(); 
using (var reader = new StreamReader(email.RawMessage())) 
using (var writer = new StringWriter()) { 
    while(true) { 
     var line = reader.ReadLine(); 
     if (line == null) break; // EOF 

     if (line != "") { 
      // Header line 
      writer.WriteLine(line); 
      continue; 
     } 

     // End of headers, insert bcc, read body, then bail 
     writer.WriteLine("Bcc: " + email.Bcc.ToString()); // or however you want to format it 
     writer.WriteLine(""); 
     writer.Write(reader.ReadToEnd()); 
     break; 
    } 

    var messageText = writer.ToString(); 
    // Do something with message text which now has Bcc: header 
} 

Answer 2

這裏是RawMessage我的VB.NET翻版（），其中包括BCC的頭。根據別人對原SO鏈接的重新編排：http://colinmackay.co.uk/2011/11/10/sending-more-than-a-basic-email-with-amazon-ses

Public Class BuildRawMailHelper 
    Private Const nonPublicInstance As BindingFlags = BindingFlags.Instance Or BindingFlags.NonPublic 

    Private Shared ReadOnly _mailWriterContructor As ConstructorInfo 
    Private Shared ReadOnly _sendMethod As MethodInfo 
    Private Shared ReadOnly _closeMethod As MethodInfo 
    Private Shared ReadOnly _writeHeadersMethod As MethodInfo 

    Shared Sub New() 
     Dim systemAssembly As Assembly = GetType(SmtpClient).Assembly 
     Dim mailWriterType As Type = systemAssembly.[GetType]("System.Net.Mail.MailWriter") 

     _mailWriterContructor = mailWriterType.GetConstructor(nonPublicInstance, Nothing, {GetType(Stream)}, Nothing) 

     _sendMethod = GetType(MailMessage).GetMethod("Send", nonPublicInstance) 

     _closeMethod = mailWriterType.GetMethod("Close", nonPublicInstance) 

     _writeHeadersMethod = mailWriterType.GetMethod("WriteHeaders", nonPublicInstance) 
    End Sub 

    Public Shared Function ConvertMailMessageToMemoryStream(message As MailMessage) As MemoryStream 
     Using memoryStream As New MemoryStream() 
      Dim mailWriter As Object = _mailWriterContructor.Invoke(New Object() {memoryStream}) 

      ' BCC is not output in headers by Send method, so we add it in manually 
      If message.Bcc.Any Then 
       Dim bccHeaders As New NameValueCollection() 
       bccHeaders.Add("BCC", String.Join(", ", message.Bcc.Select(Function(x) x.ToString()))) 
       _writeHeadersMethod.Invoke(mailWriter, nonPublicInstance, Nothing, {bccHeaders, False}, Nothing) 
      End If 

      ' See http://stackoverflow.com/questions/9595440/getting-system-net-mail-mailmessage-as-a-memorystream-in-net-4-5-beta 
      _sendMethod.Invoke(message, nonPublicInstance, Nothing, {mailWriter, True, True}, Nothing) 

      _closeMethod.Invoke(mailWriter, nonPublicInstance, Nothing, {}, Nothing) 

      Return memoryStream 
     End Using 
    End Function 
End Class