c# - StreamWriter 不写入文件

Question

我有一种方法可以将文件作为附件发送。我使用 StreamWriter 和 MemoryStream 来创建附件。代码如下:

public void ComposeEmail(string from, string to, SmtpClient client)
    {
        MailMessage mm = new MailMessage(from, to, "Otrzymałeś nowe zamówienie od "+from , "Przesyłam nowe zamówienie na sprzęt");
        mm.BodyEncoding = UTF8Encoding.UTF8;
        mm.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure;
        // Adding attachment:

        using (var ms = new System.IO.MemoryStream())
        {
            using (var writer = new System.IO.StreamWriter(ms))
            {
                writer.Write("Hello its my sample file");
                writer.Flush();

                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";

                mm.Attachments.Add(attach);
                try
                {
                    client.Send(mm);
                }
                catch (SmtpException e)
                {
                    Console.WriteLine(e.ToString());
                }
            }
        }
    }

正如您在这些行中看到的那样，我写到"file":

writer.Write("Hello its my sample file");
writer.Flush();

在调试时我可以看到 MemoryStream 的长度为 24(就像写入它的字符串的长度)。但是邮箱里收到的文件是空的。

我做错了什么？

Answer 1

尝试倒回流:

writer.Flush();
ms.Position = 0; // <===== here

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);

否则stream还是会定位到最后，从那里读取会立即报EOF。