将文件从MemoryStream附加到C＃中的MailMessage

我正在编写一个程序将文件附加到电子邮件。目前，我正在将使用的文件保存FileStream到磁盘中，然后使用

System.Net.Mail.MailMessage.Attachments.Add(
    new System.Net.Mail.Attachment("file name")); 

我不想将文件存储在磁盘中，我想将文件存储在内存中，然后从内存流中将其传递给Attachment。

这是示例代码。

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();

编辑1

您可以通过System.Net.Mime.MimeTypeNames指定其他文件类型，例如 System.Net.Mime.MediaTypeNames.Application.Pdf

根据Mime类型，您需要在FileName中指定实例扩展名"myFile.pdf"

有点晚了-但希望仍然对那里的人有用：-

这是用于发送内存中字符串作为电子邮件附件（在这种情况下为CSV文件）的简化代码段。

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);
}

在消息发送之后，才应丢弃StreamWriter和基础流（以避免ObjectDisposedException: Cannot access a closed Stream）。

由于我在任何地方都找不到对此的确认，因此我测试了处理MailMessage和/或Attachment对象是否可以按预期发生的方式处理加载到其中的流。

在以下测试中确实显示出，当处理MailMessage时，还将处理所有用于创建附件的流。因此，只要您处理MailMessage，创建它的流就不需要处理了。

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);

如果您实际上要添加.pdf，我发现有必要将内存流的位置设置为零。

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);

如果您要做的只是附加一个字符串，则只需两行即可完成：

mail.Attachments.Add(Attachment.CreateAttachmentFromString("1,2,3", "text/csv");
mail.Attachments.Last().ContentDisposition.FileName = "filename.csv";

我无法将我们的邮件服务器与StreamWriter一起使用。
我想也许是因为使用StreamWriter您缺少了许多文件属性信息，也许我们的服务器不喜欢丢失的内容。
使用Attachment.CreateAttachmentFromString（），它创建了我需要的一切，并且效果很好！

否则，建议您取出内存中的文件，然后使用MemoryStream（byte []）打开它，然后一起跳过StreamWriter。

之所以落在这个问题上，是因为我需要附加通过代码生成的Excel文件，并且该文件可以作为MemoryStream。我可以将其附加到邮件中，但是它以64字节文件的形式发送，而不是原来的6KB。因此，对我有用的解决方案是：

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);

设置attachment.ContentDisposition.Size让我发送带有正确附件大小的邮件的值。

使用其他OPEN内存流：

lauch pdf的示例，并在MVC4 C＃控制器中发送pdf

        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);
    }

我认为这段代码将帮助您：

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();
    }
  }
}