将 MemoryStream 中的文件附加到 C# 中的 MailMessage

Question

我正在编写一个程序将文件附加到电子邮件。目前我正在使用 FileStream 将文件保存到磁盘中，然后我使用“

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”，并从内存流将其传递给 Attachment< /代码>。

Answer 1

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

基于Mime类型< /strong> 您需要在文件名中指定正确的扩展名，例如 "myFile.pdf"

Answer 2

有点晚了 - 但希望对那里的人仍然有用：-

这是一个简化的代码片段，用于将内存中的字符串作为电子邮件附件（在本例中为 CSV 文件）发送。

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("[email protected]", "[email protected]", "Just testing", "See attachment..."))
{
    writer.WriteLine("Comma,Separated,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);
}

StreamWriter 和底层流在消息发送之前不得被释放（以避免ObjectDisposeException：无法访问已关闭的 Stream）。

Answer 3

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 对象是否会按照我的预期处理加载到其中的流。

通过以下测试确实可以看出，当 MailMessage 被释放时，所有用于创建附件的流也将被释放。因此，只要您处理 MailMessage，用于创建它的流就不需要再进行其他处理。

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);

Answer 4

如果您确实想添加.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);

Answer 5

如果您所做的只是附加一个字符串，您只需 2 行即可完成：

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

我无法使用带有 StreamWriter 的邮件服务器让我的字符串工作。
我想也许是因为使用 StreamWriter 你丢失了很多文件属性信息，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工作得很好！

否则，我建议获取内存中的文件并使用 MemoryStream(byte[]) 打开它，并一起跳过 StreamWriter。

Answer 6

我之所以提出这个问题，是因为我需要附加一个通过代码生成的 Excel 文件，该文件可作为 MemoryStream 使用。我可以将它附加到邮件消息中，但它是作为 64 字节文件发送的，而不是按其本来的意思是 ~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 的值让我发送具有正确附件大小的邮件。

Answer 7

使用其他开放内存流：

在 MVC4 C# 控制器中启动 pdf 并发送 pdf 的示例

        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);
    }

Answer 8

我假设当您处理 MailMessage 时，内存流也会被处理，正如上面的一位小伙子所提到的。较晚进入，并且存在流太长的内存流异常。当然，我并没有处理我的邮件消息。因此，这可能会有所帮助，我正在发送多文件附件：

    public void SendEmail(EmailDao mail)
    {
        try
        {
            //Send Email:
            var networkCredentials = new NetworkCredential { UserName = _businessSmtpDetails.GetSection("NetworkUsername").Value, Password = _businessSmtpDetails.GetSection("NetworkPassword").Value };
            var smtpServer = new SmtpClient(_businessSmtpDetails.GetSection("SmtpServer").Value);
            smtpServer.Credentials = networkCredentials;

            var mailMessage = new MailMessage();

            mailMessage.From = new MailAddress(_businessSmtpDetails.GetSection("BusinessEmail").Value);
            mailMessage.Body = mail.EmailBody;
            mailMessage.Subject = @"From " + mail.EmailFrom + " " + mail.EmailSubject;
            var fileStream = new FileInfo("/images/attachement");
            MemoryStream memoryStream = null;
            if (mail.Attachment != null)
            {
                memoryStream = new MemoryStream();
                ReadFileAttachment(mail.Attachment, memoryStream);
                memoryStream.Seek(0, SeekOrigin.Begin);
                System.Net.Mime.ContentType ct = new System.Net.Mime.ContentType(System.Net.Mime.MediaTypeNames.Text.Plain);
                var attached = new Attachment(memoryStream, mail.Attachment.FileName, ct.MediaType);
                mailMessage.Attachments.Add(attached);
            }
            if (mail.Attachments != null && mail.Attachments.Length > 0)
            {
                foreach (var attachment in mail.Attachments)
                {
                    memoryStream = new MemoryStream();
                    ReadFileAttachment(attachment, memoryStream);
                    memoryStream.Seek(0, SeekOrigin.Begin);
                    System.Net.Mime.ContentType ct = new System.Net.Mime.ContentType(System.Net.Mime.MediaTypeNames.Text.Plain);
                    var attached = new Attachment(memoryStream, mail.Attachment.FileName, ct.MediaType);
                    mailMessage.Attachments.Add(attached);
                }
            }
            mail.EmailTo += string.Format(";{0}", _businessSmtpDetails.GetSection("BusinessEmail").Value);
            Array.ForEach<string>(mail.EmailTo.Split(new char[] { ',', ';' }, StringSplitOptions.RemoveEmptyEntries), (p) =>
            {
                mailMessage.To.Add(p);
            });
            smtpServer.Send(mailMessage);
            memoryStream.Close();
            mailMessage.Dispose();
        }
        catch (Exception e)
        {
            throw e;
        }
    }

    private MemoryStream ReadFileAttachment(IFormFile attacment, MemoryStream memoryStream)
    {
        var bytes = new byte[4096];
        var bytesRead = 0;
        while ((bytesRead = attacment.OpenReadStream().Read(bytes, 0, bytes.Length)) > 0)
        {
            memoryStream.Write(bytes, 0, bytesRead);
            memoryStream.Flush();
        }
        return memoryStream;
    }

Answer 9

我认为这段代码会对您有所帮助：

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();
    }
  }
}