Question

我正在尝试使用C＃发送带附件的电子邮件。这是我的方法：

public void SendEmail(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:

        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();

        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());
        }
        ms.Close();
    }

stacktrace指向这一行：

client.Send(mm);

问题是由这一行引起的：

writer.Dispose();

为什么我在使用它写入MemoryStream之后无法立即处理此元素？以后不会在代码中使用此元素。

Answer 1

在编写器上调用Dispose也会释放底层流。发送电子邮件后，您必须同时处理编写者和流。您可以通过将代码包装在两个using语句中来实现这一目的。

    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());
         }
       }
    }

Answer 2

使用阻止，如评论中所建议的那样：

//...
using(System.IO.MemoryStream ms = new System.IO.MemoryStream())
{   
    using(System.IO.StreamWriter 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);
        client.Send(mm);

    }
}

Answer 3

当client.Send尝试发送时，显然会显示Attachment，其中MemoryStream指向已被StreamWriter关闭的ms.CanRead。您可以通过检查writer.Dispose()来验证这一点。它将返回false。

访问已关闭的流会抛出异常，这就是您所遇到的情况。解决它只是摆脱MemoryStream，因为没有任何东西可以用{{1}}处理或在你完成工作后处理它。

发送附件时无法访问封闭的流

3 个答案: