参数 1：无法从 'System.Threading.Tasks.Task<Project.Models.Booking>' 转换为 Project.Models.Booking

Question

我正在做学校项目，我正在尝试在我的存储库 类 中实现异步方法，但在我的 API 中遇到了 POST 方法的错误: 参数 1：无法从 'System.Threading.Tasks.Task' 转换为 Project.Models.Booking。

有人可以帮我解决这个错误吗？

这是我的存储库方法的样子：

    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;
    }

这就是我的 Post 方法的样子：

 [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();
        }

我在以下位置收到错误消息：uw.Services.AddBooking(uw.Bookings.CreateBooking(booking), inBooking.service.ServiceId);`

Answer 1

trying to implement asynchronous methods in my repository classes

使事物异步的最好方法不是来自 "outside in"。也就是说，您不想从控制器操作开始并说 "how can I make this asynchronous?"。相反，您想从 lowest-level API 开始并说 "this should be asynchronous"（即 I/O-based），并让异步从那里发展出来。

如果 Add 实际上执行数据库插入，那么这将是第一个异步方法。然后你 await 你的 AddAsync 方法，异步从 AddAsync 增长到 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();
}

另一方面，如果实际与数据库通信的是 Complete 方法，那么 应该是异步的。在这种情况下 Add 纯粹是一个 in-memory 操作，而 Complete 是保存所有数据库更新的操作。因此，在 将 Complete 转换为 CompleteAsync 之后，您的代码将如下所示：

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();
}