尝试等待“（等待）Windows.Foundation.IAsyncOperation”时出现语法错误

Question

I'm getting a really confusing error Message from Visual Studio, telling me I cannot use "await" on a method that is marked "(awaitable)." Here is the full message:

Error 1 The 'await' operator can only be used within an async method. Consider marking this method with the 'async' modifier and changing its return type to 'Task<Windows.Phone.Media.Capture.AudioVideoCaptureDevice>'

And here is my code:

    private AudioVideoCaptureDevice SetupController()
    {
        CameraSensorLocation Location = CameraSensorLocation.Back;
        AudioVideoCaptureDevice CameraController = await AudioVideoCaptureDevice.OpenAsync(Location, AudioVideoCaptureDevice.GetAvailableCaptureResolutions(Location).First());

        CameraController.SetProperty(KnownCameraAudioVideoProperties.VideoTorchMode, VideoTorchMode.On);

        return CameraController;
    }

The error is with this line:

AudioVideoCaptureDevice CameraController = await AudioVideoCaptureDevice.OpenAsync(Location, AudioVideoCaptureDevice.GetAvailableCaptureResolutions(Location).First());

Answer 1

When you are using await - you must use it within a method that supports asynchronous operation. And as you are returning a value - make it a Task<>

Try to make your method async:

private async Task<AudioVideoCaptureDevice> SetupController()
{
  // your code
}

And as it's now asynchronous then use it:

AudioVideoCaptureDevice myDevice = await SetupController(); // which should also be run from async method