Attach a file from MemoryStream to a MailMessage in C

Question

I am writing a program to attach a file to email  Currently I am saving file using FileStream into disk  and then I use   System Net Mail MailMessage Attachments Add      new System Net Mail Attachment  file name        I do not want to store file in disk  I want to store file in memory and from memory stream pass this to Attachment

User · Answer

If all you re doing is attaching a string  you could do it in just 2 lines   mail Attachments Add Attachment CreateAttachmentFromString  1 2 3    text csv    mail Attachments Last   ContentDisposition FileName    filename csv     I wasn t able to get mine to work using our mail server with StreamWriter  I think maybe because with StreamWriter you re missing a lot of file property information and maybe our server didn t like what was missing  With Attachment CreateAttachmentFromString   it created everything I needed and works great   Otherwise  I d suggest taking your file that is in memory and opening it using MemoryStream byte     and skipping the StreamWriter all together

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A bit of a late entry - but hopefully still useful to someone out there -  Here s a simplified snippet for sending an in-memory string as an email attachment  a CSV file  in this particular case    using  var stream   new MemoryStream    using  var writer   new StreamWriter stream         using UTF-8 encoding by default using  var mailClient   new SmtpClient  localhost   25   using  var message   new MailMessage  me example com    you example com    Just testing    See attachment             writer WriteLine  Comma Seperated Values            writer Flush        stream Position   0         read from the start of what was written      message Attachments Add new Attachment stream   filename csv    text csv          mailClient Send message       The StreamWriter and underlying stream should not be disposed until after the message has been sent  to avoid ObjectDisposedException  Cannot access a closed Stream

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If you actually want to add a  pdf  I found it necessary to set the position of the memory stream to Zero   var memStream   new MemoryStream yourPdfByteArray   memStream Position   0  var contentType   new System Net Mime ContentType System Net Mime MediaTypeNames Application Pdf   var reportAttachment   new Attachment memStream  contentType   reportAttachment ContentDisposition FileName    yourFileName pdf   mailMessage Attachments Add reportAttachment

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I think this code will help you   using System  using System Data  using System Configuration  using System Web  using System Web Security  using System Web UI  using System Web UI WebControls  using System Web UI WebControls WebParts  using System Web UI HtmlControls  using System Net Mail   public partial class  Default   System Web UI Page     protected void Page Load object sender  EventArgs e              protected void btnSubmit Click object sender  EventArgs e          try             MailAddress SendFrom   new MailAddress txtFrom Text         MailAddress SendTo   new MailAddress txtTo Text          MailMessage MyMessage   new MailMessage SendFrom  SendTo          MyMessage Subject   txtSubject Text        MyMessage Body   txtBody Text         Attachment attachFile   new Attachment txtAttachmentPath Text         MyMessage Attachments Add attachFile          SmtpClient emailClient   new SmtpClient txtSMTPServer Text         emailClient Send MyMessage          litStatus Text    Message Sent             catch  Exception ex              litStatus Text   ex ToString

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use OTHER OPEN memorystream   example for lauch pdf and send pdf in MVC4 C  Controller          public void ToPdf string uco  int idAudit                Response Clear            Response ContentType    application octet-stream           Response AddHeader  content-disposition    attachment filename  Document pdf            Response Buffer   true          Response Clear               get the memorystream pdf         var bytes   new MisAuditoriasLogic   ToPdf uco  idAudit  ToArray             Response OutputStream Write bytes  0  bytes Length           Response OutputStream Flush                 public ActionResult ToMail string uco  string filter  int  page  int idAudit  int  full                   get the memorystream pdf         var bytes   new MisAuditoriasLogic   ToPdf uco  idAudit  ToArray             using  var stream   new MemoryStream bytes           using  var mailClient   new SmtpClient    YOUR SERVER     25           using  var message   new MailMessage    SENDER        RECEIVER      Just testing    See attachment                              stream Position   0               Attachment attach   new Attachment stream  new System Net Mime ContentType  application pdf                 attach ContentDisposition FileName    test pdf                message Attachments Add attach                mailClient Send message                      ViewBag errMsg    Documento enviado             return Index uco  filter  page  idAudit  full

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Here is the sample code   System IO MemoryStream ms   new System IO MemoryStream    System IO StreamWriter writer   new System IO StreamWriter ms   writer Write  Hello its my sample file    writer Flush    writer Dispose    ms Position   0   System Net Mime ContentType ct   new System Net Mime ContentType System Net Mime MediaTypeNames Text Plain   System Net Mail Attachment attach   new System Net Mail Attachment ms  ct   attach ContentDisposition FileName    myFile txt       I guess you know how to send email with an attachment    after sending email ms Close      Edit 1  You can specify other file types by System Net Mime MimeTypeNames like System Net Mime MediaTypeNames Application Pdf  Based on Mime Type you need to specify correct extension in FileName for instance  myFile pdf

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I landed on this question because I needed to attach an Excel file I generate through code and is available as MemoryStream  I could attach it to the mail message but it was sent as 64Bytes file instead of a  6KB as it was meant  So  the solution that worked for me was this   MailMessage mailMessage   new MailMessage    Attachment attachment   new Attachment myMemorySteam  new ContentType MediaTypeNames Application Octet     attachment ContentDisposition FileName    myFile xlsx   attachment ContentDisposition Size   attachment Length   mailMessage Attachments Add attachment     Setting the value of attachment ContentDisposition Size let me send messages with the correct size of attachment

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Since I couldn t find confirmation of this anywhere  I tested if disposing of the MailMessage and or the Attachment object would dispose of the stream loaded into them as I expected would happen   It does appear with the following test that when the MailMessage is disposed  all streams used to create attachments will also be disposed   So as long as you dispose your MailMessage the streams that went into creating it do not need handling beyond that   MailMessage mail   new MailMessage      Create a MemoryStream from a file for this test MemoryStream ms   new MemoryStream File ReadAllBytes   C  temp test gif      mail Attachments Add new System Net Mail Attachment ms   test gif     if  mail Attachments 0  ContentStream    ms  Console WriteLine  Streams are referencing the same resource    Console WriteLine  Stream length      mail Attachments 0  ContentStream Length      Dispose the mail as you should after sending the email mail Dispose      --Or you can dispose the attachment itself   mm Attachments 0  Dispose     Console WriteLine  This will throw a  Cannot access a closed Stream   exception      ms Length

[c#] Attach a file from MemoryStream to a MailMessage in C#

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