system.net.mail 附件的常见问题

Question

我在 VB.net 项目上的附件内存流遇到了常见问题。我正在调用一个共享成员 (SendMail)，传入一个客户对象和一个要作为附件发送的文件的内存流。在“SendMail”中，它调用两个单独的函数来准备一封常规电子邮件，另一个用于准备数字签名电子邮件。我遇到的问题是我收到了完美的数字签名电子邮件，但是，在常规电子邮件中，附件为空白，并且已附加文件名 (64 B)。如果我禁用数字签名的部分，则常规邮件可以正常工作。看起来内存流在数字签名中的某个地方发生了变化。

进行调用

mailHelper.SendMail(cust, attachment)

这是我如何使用 mailHelper 类

Public Shared Sub SendEmail(ByVal cust As Customer, ByVal attachment As MemoryStream)

  Dim messages As New List(Of MailMessage)
  messages.Add(CreateUnSignedMail(cust,attachment)
  messages.Add(CreateSignedMail(cust,attachment)
  SendSMTPMail(messages)
End Sub

Private Shared Function CreateUnSignedMail(ByVal cust As Customer, ByVal attachment As MemoryStream) As MailMessage

Dim eMail As New MailMessage()
        With eMail
            .//Normal properties set (like to, from etc)

            .Attachments.Add(New Attachment(attachment, "someFilename.doc")
        End With
        Return eMail
End Function

Private Shared Function CreateSignedMail(ByVal cust As Customer, ByVal attachment As MemoryStream) As MailMessage

Dim eMail As New SecureMailMessage()
        With eMail
            .//Normal properties set (like to, from etc)

            .Attachments.Add(New  SecureAttachment(attachment, "someFilename.doc")
        End With
        Return eMail
End Function


Private Shared Sub SendSMTPMail(ByVal messages As List(Of System.Net.Mail.MailMessage))
        Dim smtp As New SmtpClient("myServer")
        Try
            With smtp
                .//Additional properties set

                For Each email In messages
                    .Send(email)
                Next

            End With

        Catch ex As Exception
            //Log error to file.
            Logger.Log.Error("SMTP Error", ex)
            Throw
        End Try
End Sub

如果我尝试以下操作，它工作正常，但是，这是正确的解决方案吗？

messages.Add(SendUnSignedMail(cust, New MemoryStream(attachment.ToArray())))
messages.Add(SendSignedMail(cust, New MemoryStream(attachment.ToArray())))

Answer 1

假设您已经解决了这个问题，因为得到答案的延迟，但无论如何，这是我的尝试...

有很多重载来创建附件，它们都不符合您初始化附件的方式。

创建附件时，第二个参数必须为 NULL 或标识附件的有效 MIME 类型。

希望这有帮助。