Joindre plusieurs fichiers à un programme électronique sans écrire sur le disque

Question

Notre projet a des fichiers stockés dans un serveur sql db sous forme de blobs. Je voudrais obtenir les fichiers de la base de données et joindre plusieurs fichiers à un courriel sans écrire sur le disque.

C'est ce que j'ai jusqu'à présent (tout fonctionne bien, sans pièces jointes):

// 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; 
} 

Je reçois les erreurs suivantes:

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) 

j'ai copié la plupart du code de flux d'exemples que j'ai trouvés sur le web.

Answer 1

Vous avez trouvé une raison pour ne pas implémenter un bloc using: lorsque vous allez toujours utiliser l'objet après la fermeture du bloc. Prenez le MemoryStream dans le bloc using.