PdfGenerator EmailMessage EmailAttachment - 无法访问已关闭的流

Question

尝试附加 System.IO.MemoryStream EmailAttachment 并将其发送到 EmailMessage 时，抛出错误 System.ObjectDisposedException 和消息 Cannot access a closed Stream。正在使用 HtmlRenderer.PdfSharp 生成附件。附加和发送是在 using 语句中完成的。

using (MemoryStream ms = new MemoryStream())
{
    var pdf = PdfGenerator.GeneratePdf("<html><body>foo</body></html>", PdfSharp.PageSize.Letter);
    // 2nd argument is to NOT close stream
    pdf.Save(ms, false);

    EmailMessage em = new EmailMessage();
    em.EmailFormat = EmailFormatEnum.Html;
    em.From = "no-reply@foo.com";
    em.Recipients = "foo.bar@baz.net";
    em.Subject = "Attachment Name";
    em.Body = "There is an attachment";

    var attachment = new EmailAttachment(ms, "foo.pdf");
    em.Attachments.Add(attachment);

    // SiteContext.CurrentSiteName argument is just a site name required for Kentico CMS
    // true argument is send immediately
    EmailSender.SendEmail(SiteContext.CurrentSiteName, em, true);    
}

如果我改为执行以下操作，只要我不尝试在 try 块内 ms.Dispose() 就不会发生错误：

MemoryStream ms = new MemoryStream();
try
{
    var pdf = PdfGenerator.GeneratePdf(html, PdfSharp.PageSize.A4);
    pdf.Save(ms, false);

    EmailMessage em = new EmailMessage();
    em.EmailFormat = EmailFormatEnum.Html;
    em.From = "no-reply@foo.com";
    em.Recipients = "foo.bar@baz.net";
    em.Subject = "Attachment Name";
    em.Body = "There is an attachment";

    var attachment = new EmailAttachment(ms, "foo.pdf");
    em.Attachments.Add(attachment);

    EmailSender.SendEmail(SiteContext.CurrentSiteName, em, true);
}
catch (Exception)
{
    ms.Dispose();
}

第二种方法的问题是 MemoryStream 没有被明确处理。 MemoryStream 是否天生就是用这种方法处理的？如果将 ms.Dispose(); 放在之后，整个块都会发生相同的 Cannot access a closed Stream。这是等待发生的内存泄漏吗？如何在不关闭流的情况下处理 MemoryStream 以允许电子邮件发送附件？

这是一个需要以某种方式等待 SendEmail() 实际执行其功能的问题吗？

感谢您提供的任何帮助。

Answer 1

我不明白你为什么要在 try 块中处理 ms，通常是为了清理你使用 finally 块的变量，无论是否有异常，它都会被执行。
如果你使用 catch（那种带有 Exception 的 catch 会捕获所有异常）你不会得到错误，因为你正在捕获它们

你应该怎么做：

MemoryStream ms = new MemoryStream();
try
{
    var pdf = PdfGenerator.GeneratePdf(html, PdfSharp.PageSize.A4);
    pdf.Save(ms, false);

    EmailMessage em = new EmailMessage();
    em.EmailFormat = EmailFormatEnum.Html;
    em.From = "no-reply@foo.com";
    em.Recipients = "foo.bar@baz.net";
    em.Subject = "Attachment Name";
    em.Body = "There is an attachment";

    var attachment = new EmailAttachment(ms, "foo.pdf");
    em.Attachments.Add(attachment);

    EmailSender.SendEmail(SiteContext.CurrentSiteName, em, true);
}
catch (Exception ex)
{
    Console.WriteLine(ex.Message);
}
finally
{
ms.Dispose();
}

Answer 2

我能够使用以下代码找到解决方案。关于 SendMail() 的 sendImmediately 参数，它实际上可能更像是一个 Kentico CMS 问题。通过将其设置为 false（默认），我能够将流作为 EmailAttachment 附加，而不会在 using 语句中出现 System.ObjectDisposedException 错误。

using (MemoryStream ms = new MemoryStream())
{
    var pdf = PdfGenerator.GeneratePdf(html, PdfSharp.PageSize.Letter);
    pdf.Save(ms, false);

    EmailMessage em = new EmailMessage();
    em.EmailFormat = EmailFormatEnum.Html;
    em.From = "no-reply@foo.com";
    em.Recipients = "foo.bar@baz.net";
    em.Subject = "Attachment Name";
    em.Body = "There is an attachment.";

    var attachment = new EmailAttachment(ms, "foo.pdf");
    em.Attachments.Add(attachment);

    // default sendImmediately of false
    EmailSender.SendEmail(SiteContext.CurrentSiteName, em);
}

Answer 3

好吧，您只需要在从 Kentico 访问它之前关闭流，即：

using (MemoryStream ms = new MemoryStream())
{
    var pdf = PdfGenerator.GeneratePdf(html, PdfSharp.PageSize.Letter);
    pdf.Save(ms, false);
}

然后是电子邮件部分：

        EmailMessage em = new EmailMessage();
        em.EmailFormat = EmailFormatEnum.Html;
        em.From = "no-reply@foo.com";
        em.Recipients = "foo.bar@baz.net";
        em.Subject = "Attachment Name";
        em.Body = "There is an attachment.";
        using (MemoryStream ms = new MemoryStream())
        {
           var attachment = new EmailAttachment(ms, "foo.pdf");
           em.Attachments.Add(attachment);
        }
        EmailSender.SendEmail(SiteContext.CurrentSiteName, em);

PdfGenerator EmailMessage EmailAttachment - 无法访问已关闭的流

PdfGenerator EmailMessage EmailAttachment - Cannot access a closed Stream

c#

asp.net

webforms

kentico