Exception when sending multiple mails using dependency injection

I’m using Hangfire hosted in an ASP.NET core site as a background job processor. The email service gets a IFluentEmail instance from the DI container. When multiple email jobs are being processed at the same time I get an exception with the following stack trace:

 ---> System.Net.Mail.SmtpException: Failure sending mail.
 ---> System.InvalidOperationException: An asynchronous call is already in progress. It must be completed or canceled before you can call this method.
   at System.Net.Mail.SmtpClient.SendAsync(MailMessage message, Object userToken)
   --- End of inner exception stack trace ---
   at System.Net.Mail.SmtpClient.SendAsync(MailMessage message, Object userToken)
   at FluentEmail.Smtp.SendMailEx.SendMailExImplAsync(SmtpClient client, MailMessage message, CancellationToken token)
   at FluentEmail.Smtp.SmtpSender.SendAsync(IFluentEmail email, Nullable`1 token)
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)
   at System.Threading.Tasks.Task`1.get_Result()
   at FluentEmail.Smtp.SmtpSender.Send(IFluentEmail email, Nullable`1 token)
   at FluentEmail.Core.Email.Send(Nullable`1 token)

The problem is that the AddFluentEmail method seems to be registering the service with a scope other than Transient. The result is that the same service instance is being returned each time with the same underlying SmtpClient. The fix would be to change the registration to Transient so that a new instance is created for each request with a separate SmtpClient.

[IanLedzion]

Thanks, that makes sense. As my SMTP configuration is a bit more complex the Func overload would be more appropriate:

services.AddFluentEmail("[e-mail]")
    .AddSmtpSender(() => new SmtpClient{/* Options */});

I’ll give it a try and see what happens.

[mohamedbenlassoued]

Hello ,i have the same bug.so does this commit [https://github.com/lukencode/FluentEmail/pull/188/commits/567a7b6d48c3c0ebead0a6635c6b36da50ba34c9] resolve this problem?