我试图使用ASP.NET Core3.1和C#发送带有附件的电子邮件。 最初从数据库加载数据并将其作为内存流附加到邮件中，我可以接收邮件，但附件中的内容总是空白的。

我试过文本格式，CSV格式，PDF格式，我收到的每一个附件都是空白的，不知道我做错了什么，下面是代码，

public void SendEmail(DataTable table)   
{
    MemoryStream _oMemStream = new MemoryStream();
    StreamWriter sw = new StreamWriter(_oMemStream);
    foreach (DataColumn column in table.Columns)
    {
        sw.Write(column.ColumnName.ToString() + ",");
    }
    foreach (DataRow row in table.Rows)
    {
        for (int i = 0; i < row.ItemArray.Length; i++)
        {
            string rowText = row.ItemArray[i].ToString();
            sw.Write(rowText + ",");
        }
        sw.WriteLine();
    }

    EmailDetailsModel emDetails = new EmailDetailsModel();
    emDetails.Body = "Body Of the Mail For Email Functionality";
    emDetails.Email = "xxxx";
    emDetails.To = "xxx";
    emDetails.Subject = "Testing Email Functionality";
    emDetails.Password = "xxx";

    using (MailMessage mm = new MailMessage(emDetails.Email, emDetails.To))
    {
        _oMemStream.Position = 0;
        mm.Subject = emDetails.Subject;
        mm.Body = emDetails.Body;
        var contentType = new System.Net.Mime.ContentType(System.Net.Mime.MediaTypeNames.Application.Pdf);
        var reportAttachment = new Attachment(_oMemStream, contentType);
        reportAttachment.ContentDisposition.FileName = "yourFileName.pdf";
        mm.Attachments.Add(reportAttachment);
        mm.IsBodyHtml = false;

        using (SmtpClient smtp = new SmtpClient())
        {
            smtp.Host = "smtp.gmail.com";
            smtp.EnableSsl = true;
            NetworkCredential NetworkCred = new NetworkCredential(emDetails.Email, emDetails.Password);
            smtp.UseDefaultCredentials = true;
            smtp.Credentials = NetworkCred;
            smtp.Port = xx;
            smtp.Send(mm);
            ViewBag.Message = "Email sent.";
        }
    }
}

谢谢你的建议