参数1：无法从“ System.Threading.Tasks.Task”转换 <Project.Models.Booking> &#39;到Project.Models.Booking

Question

I'm working on school project, and I'm trying to implement asynchronous methods in my repository classes and got this error in my API for the POST-method: Argument 1: cannot convert from 'System.Threading.Tasks.Task' to Project.Models.Booking.

Can someone please help me to solve this error?

This is how my repository-method looks like:

    public async Task<Booking>CreateBooking(Booking inBooking) {
        Booking booking = new Booking();

        booking.BookingId = ApplicationDbContext.Bookings.Count();
        booking.UserName = inBooking.UserName;
        booking.UserMail = inBooking.UserMail;
        booking.UserMobile = inBooking.UserMobile;
        booking.Available = false;
        booking.StartTime = inBooking.StartTime;
        booking.EndTime = inBooking.EndTime;
        booking.Date = inBooking.Date;

        Add(booking);
        return await Task.FromResult(booking);
        //return booking;
    }

And this how my Post-method looks like:

 [Route("api/PostBooking")]
        [HttpPost]
        public async Task<IHttpActionResult> PostBooking(BookingSystemServiceBookingViewModel inBooking)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest("Invalid data");
            }

            var booking =  inBooking.booking;

            booking.StartTime = inBooking.startTime;
            booking.EndTime = inBooking.startTime.AddMinutes(inBooking.service.Duration);

             uw.Services.AddBooking(uw.Bookings.CreateBooking(booking), inBooking.service.ServiceId);
            uw.Complete();

            return Ok();
        }

I get the error message at: uw.Services.AddBooking(uw.Bookings.CreateBooking(booking), inBooking.service.ServiceId);`

Answer 1

trying to implement asynchronous methods in my repository classes

The best way to make things asynchronous is not from the "outside in". That is, you don't want to start at the controller action and say "how can I make this asynchronous?". Instead, you want to start from the lowest-level API and say "this should be asynchronous" (ie, it's I/O-based), and let asynchrony grow out from there.

If Add actually does the database insert, then that would be the first method to be made asynchronous. Then you await your AddAsync method, and the asynchrony grows from AddAsync to CreateBookingAsync :

public async Task<Booking> CreateBookingAsync(Booking inBooking) {
  Booking booking = new Booking();

  ...

  await AddAsync(booking);
  return booking;
}

[Route("api/PostBooking")]
[HttpPost]
public async Task<IHttpActionResult> PostBooking(BookingSystemServiceBookingViewModel inBooking)
{
  ...

  uw.Services.AddBooking(await uw.Bookings.CreateBookingAsync(booking), inBooking.service.ServiceId);
  uw.Complete();

  return Ok();
}

If, on the other hand, it is the Complete method that actually communicates with the database, then that is the one that should be made asynchronous. In this case Add is purely an in-memory operation, and Complete is the one that saves all the database updates. So, after you convert Complete to CompleteAsync , your code would look like:

public Booking CreateBooking(Booking inBooking) {
  Booking booking = new Booking();

  ...

  Add(booking);
  return booking;
}

[Route("api/PostBooking")]
[HttpPost]
public async Task<IHttpActionResult> PostBooking(BookingSystemServiceBookingViewModel inBooking)
{
  ...

  uw.Services.AddBooking(uw.Bookings.CreateBooking(booking), inBooking.service.ServiceId);
  await uw.CompleteAsync();

  return Ok();
}