asp.net mvc 5 asynchronous action method

Question

I have the following action method with async and await keywords:

[HttpPost]
public async Task<ActionResult> Save(ContactFormViewModel contactFormVM)
{
     if (domain.SaveContactForm(contactFormVM) > 0)// saves data in database
     {
         bool result = await SendMails(contactFormVM);//need to execute this method asynchronously but it executes synchronously
         return Json("success");
     }
         return Json("failure");
  }

    public async Task<bool> SendMails(ContactFormViewModel contactFormVM)
    {
            await Task.Delay(0);//how to use await keyword in this function?
            domain.SendContactFormUserMail(contactFormVM);
            domain.SendContactFormAdminMail(contactFormVM);
            return true;
    }

In the above code, once the database operation is finished I want to immediately return Json() result and then call the SendMails() method which should execute in the background. What changes should I make to the above code?

Answer 1

The await operator is applied to a task in an asynchronous method to suspend the execution of the method until the awaited task completes. The task represents ongoing work.

It sounds like you don't want to wait for the result of SendMails. Think of async and await as tools to consume asynchronous APIs. Specifically, it's really useful to be able to "await" for the result of an "async" task. However, if you don't care about the result of your "async" (e.g. SendMails) task, then you don't need to "await" for the result (i.e. boolean).

Instead, you can simply use Task.Run to invoke your asynchronous task.

[HttpPost]
public async Task<ActionResult> Save(ContactFormViewModel contactFormVM) {
  if (domain.SaveContactForm(contactFormVM) > 0) {// saves data in database 
    Task.Run(() => SendMails(contactFormVM));
    return Json("success");
  }
  return Json("failure");
}

public void SendMails(ContactFormViewModel contactFormVM) {
  domain.SendContactFormUserMail(contactFormVM);
  domain.SendContactFormAdminMail(contactFormVM);
}