无需写入磁盘即可将多个文件附加到programticaly的电子邮件中

Question

我们的项目将文件存储在sql server db中作为blob.我想从数据库中获取文件并将多个文件附加到电子邮件而无需写入磁盘.

这是我到目前为止(一切正常,没有附件):

// snip

List<System.Net.Mail.Attachment> attachments = null;
// Attachments is a child list of Messagebody object holding Attachment ids
MessageBody.Attachments = MessageBodyAttachmentList.GetMessageBodyAttachmentList(this.MessageBody.ID);

if (MessageBody.Attachments != null && MessageBody.Attachments.Count > 0)
{
    attachments = new List<Attachment>();

    foreach (Library.Entity.Messaging.MessageBodyAttachment att in MessageBody.Attachments)
    {
        using (MemoryStream memoryStream = new MemoryStream())
        {
            // create a new attachment
            Library.Attachments.Attachment attachment = Library.Attachments.Attachment.GetAttachment(att.AttachmentID);

            byte[] contentAsBytes = attachment.FileData;// FileData holds byte[] that is the contents of the file
            memoryStream.Write(contentAsBytes, 0, contentAsBytes.Length);
            memoryStream.Seek(0, SeekOrigin.Begin);

            // content type for file info
            ContentType contentType = new ContentType();
            contentType.MediaType = MediaTypeNames.Application.Octet;
            contentType.Name = attachment.FileName;

            // create the .Net specific attachment
            Attachment netAttachment = new Attachment(memoryStream, contentType);
            attachments.Add(netAttachment);

            memoryStream.Position = 0;
        }
    }
}

response = message.SendMessage(_recipient, _sender, _cc, _bcc, MessageBody.Subject, MessageBody.Body, true, attachments);
// snip

public string SendMessage(string to, string from, string cc, string bcc, string subject, string body, bool IsHtml,  List<Attachment> attachments)
{
    string response = String.Empty;
    System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage(from, to, subject, body);

    // Add the attachments
    if (attachments != null)
    {
        foreach (Attachment a in attachments)
            message.Attachments.Add(a);
    }

    message.IsBodyHtml = IsHtml;

    if (IsHtml)
    {
        // snip
    }

    try
    {
        _client.Timeout = 500000;
        _client.Send(message);
    }
    catch (SmtpException smtpex)
    {
        response = smtpex.Message;
    }
    catch (System.Exception ex)
    {
        response = ex.Message;
    }
    return response;
}

我收到以下错误:

exception message: Failure sending mail.
source: System
stack trace:
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   at MyCompany.Shared.Email.SMTPMessage.SendMessage(String to, String from, String cc, String bcc, String subject, String body, Boolean IsHtml, List`1 attachments) in C:\svn_repos\branches\2010.02.28\Net\Common\Shared\Email\SMTPMessage.cs:line 116

inner exception msg: Cannot access a closed Stream.
inner source: mscorlib
inner targetsite: {Void StreamIsClosed()}
inner stack trace:
   at System.IO.__Error.StreamIsClosed()
   at System.IO.MemoryStream.Read(Byte[] buffer, Int32 offset, Int32 count)
   at System.Net.Mime.MimePart.Send(BaseWriter writer)
   at System.Net.Mime.MimeMultiPart.Send(BaseWriter writer)
   at System.Net.Mail.Message.Send(BaseWriter writer, Boolean sendEnvelope)
   at System.Net.Mail.MailMessage.Send(BaseWriter writer, Boolean sendEnvelope)
   at System.Net.Mail.SmtpClient.Send(MailMessage message)

我从网上找到的例子中复制了大部分流代码.

Answer 1

你找到了一个不实现using块的理由:当块退出后你仍然要使用该对象时.就拿MemoryStream出来的using块.