c#之发送到多个电子邮件地址时，ASP.NET C# 电子邮件附件最终变为 0 字节

我有一个将电子邮件发送到列表的例程，如下所示，我已经对其进行了测试。我收到的第一封电子邮件没问题，但第二封电子邮件的字节数比实际文件呈现的字节数少，无法打开。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进行了不正确的解码。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 
    { 
    } 

请您参考如下方法:

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);