ASP.NET C# 电子邮件附件在发送到多个电子邮件地址时最终变为 0 字节

Question

我有这个例程将电子邮件发送到如下列表，并且我已经对其进行了测试。我收到的第一封电子邮件很好，但第二封电子邮件的字节数少于实际文件导致其打开时损坏的字节数。我怎样才能使每个电子邮件附件都能正确发送而不发送任何 0 字节附件？我通过 ASP.NET C# webform 将附件直接发送给收件人，但大多数 PDF 附件都通过错误消息解码不正确。这是页面的主要电子邮件代码：

if (emailIsValid(EmailToSend))
{
    string TheSubject = SubjectTxt.Text;
    string TheBody = "Dear " + FirstName + ",<br/><br/>" + MessageTxt.Text;
    TheBody = TheBody + " EMail Body "
    string BodyTxt = TheBody.Replace(Environment.NewLine, "<br />");

    MailMessage mailObj = new MailMessage(
        "noreply@company.com", EmailToSend, TheSubject, BodyTxt);
    SmtpClient SMTPServer = new SmtpClient("unknown.company.com");

    string RPT = FromTxt.Text;
    mailObj.ReplyToList.Add(RPT);
    mailObj.BodyEncoding = System.Text.Encoding.UTF8;
    mailObj.IsBodyHtml = true;


    string filePath = txtAttachment.PostedFile.FileName;
    string filename = Path.GetFileName(filePath);
    string ext = Path.GetExtension(filename);
    string contenttype = String.Empty;

    //Set the contenttype based on File Extension
    switch (ext)
    {
        case ".doc":
            contenttype = "application/vnd.ms-word";
            break;
        case ".docx":
            contenttype = "application/vnd.ms-word";
            break;
        case ".xls":
            contenttype = "application/vnd.ms-excel";
            break;
        case ".xlsx":
            contenttype = "application/vnd.ms-excel";
            break;
        case ".ppt":
            contenttype = "application/vnd.ms-powerpoint";
            break;
        case ".pptx":
            contenttype = "application/vnd.ms-powerpoint";
            break;
        case ".jpg":
            contenttype = "image/jpg";
            break;
        case ".png":
            contenttype = "image/png";
            break;
        case ".gif":
            contenttype = "image/gif";
            break;
        case ".pdf":
            contenttype = "application/pdf";
            break;
        case ".csv":
            contenttype = "text/csv";
            break;
        case ".txt":
            contenttype = "text/csv";
            break;
        default:
            contenttype = "Unknown Content Type";
            break;


    }

    if (txtAttachment.PostedFile != null && contenttype != "Unknown Content Type")
    {
        try
        {
            string strFileName =
            System.IO.Path.GetFileName(txtAttachment.PostedFile.FileName);
            Attachment attachFile =
            new Attachment(txtAttachment.PostedFile.InputStream, strFileName, contenttype);                                           
            mailObj.Attachments.Add(attachFile);
        }
        catch
        {

        }
    }

    try
    {
        SMTPServer.Send(mailObj);

        SqlConnection con2 = new SqlConnection(CS);

        con2.Open();

        DateTime now = DateTime.Now;
    }
catch
    {
    }

Answer 1

之前

Attachment attachFile =
        new Attachment(txtAttachment.PostedFile.InputStream, strFileName, contenttype);

尝试重置流光标，如下所示：

txtAttachment.PostedFile.InputStream.Position = 0;
Attachment attachFile =
        new Attachment(txtAttachment.PostedFile.InputStream, strFileName, contenttype);