System.ObjectDisposedException在使用SMTPCLIENT发送电子邮件时（Fluent-Email）

Question

当我尝试使用Fluent-Email库中的一个.NET Core 6.0项目中发送电子邮件时，我将获得system.ObjectDisposedexception：

System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'System.Net.Mail.SmtpClient'.
   at System.Net.Mail.SmtpClient.SendAsync(MailMessage message, Object userToken)
   at FluentEmail.Smtp.SendMailEx.SendMailExImplAsync(SmtpClient client, MailMessage message, CancellationToken token)

我尝试注入smtpclient > 瞬态， scoped ，作为 singleton ，但没有解决此问题的选项。

DI代码：

  var smtpClient = new SmtpClient(smtpSenderOptions.Host, smtpSenderOptions.Port)
                {
                    EnableSsl = smtpSenderOptions.EnableSsl
                };

                services.AddSingleton(instance => smtpClient);

用法（摘自Fluent-Email库（ https://github.com/lukencode/lukencode/lukencode/fluentemail ））：

    
    // Taken from https://stackoverflow.com/questions/28333396/smtpclient-sendmailasync-causes-deadlock-when-throwing-a-specific-exception/28445791#28445791
    // SmtpClient causes deadlock when throwing exceptions. This fixes that.
    public static class SendMailEx
    {
        public static Task SendMailExAsync(
            this SmtpClient @this,
            MailMessage message,
            CancellationToken token = default(CancellationToken))
        {
            // use Task.Run to negate SynchronizationContext
            return Task.Run(() => SendMailExImplAsync(@this, message, token));
        }

        private static async Task SendMailExImplAsync(
            SmtpClient client,
            MailMessage message,
            CancellationToken token)
        {
            token.ThrowIfCancellationRequested();

            var tcs = new TaskCompletionSource<bool>();
            SendCompletedEventHandler handler = null;
            Action unsubscribe = () => client.SendCompleted -= handler;

            handler = async (_, e) =>
            {
                unsubscribe();

                // a hack to complete the handler asynchronously
                await Task.Yield();

                if (e.UserState != tcs)
                    tcs.TrySetException(new InvalidOperationException("Unexpected UserState"));
                else if (e.Cancelled)
                    tcs.TrySetCanceled();
                else if (e.Error != null)
                    tcs.TrySetException(e.Error);
                else
                    tcs.TrySetResult(true);
            };

            client.SendCompleted += handler;
            try
            {
                client.SendAsync(message, tcs);
                using (token.Register(() =>
                {
                    client.SendAsyncCancel();
                }, useSynchronizationContext: false))
                {
                    await tcs.Task;
                }
            }
            finally
            {
                unsubscribe();
            }
        }
    }

我的代码调用库：

  var response = await _fluentEmail
                .Subject(emailContents.Subject)
                .To(emailContents.To)
                .Attach(attachments)
                .UsingTemplate(template, emailContents)
                .SendAsync(cancellationToken);

Answer 1

Fluent-Email提供的扩展名确实将这些类注射为Singleton和我确实使用了另一个生命周期，因此发生了这个问题。

因此，我也忘了使用system.ObjectDisposedexception使用Singleton的所有依赖项的依赖项注入容器配置，因为我正在使用自定义实现fluentemail.smtp.sendmail.sendmailmail.sendmailmailex.sendmailmaileximpleximpleximpleximplasync 。

在DI扩展中超越了其他依赖关系之后，它起作用了。