FromBluetoothAddressAsync IAsyncOperation does not contain a definition for 'GetAwaiter' error

Question

I am working on a simple BLE UWP. I've been referring to "Windows UWP connect to BLE device after discovery", working in Visual Studio 2017.

The core code I have is:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Windows.Threading;


using Windows.Devices.Bluetooth.Advertisement;
using Windows.Devices.Bluetooth;
using Windows.Devices;
using Windows.Foundation;
using Windows;

namespace WindowsFormsApp2
{
    public partial class Form1 : Form
    {

        private BluetoothLEAdvertisementWatcher watcher;

        public Form1()
        {

            InitializeComponent();
            watcher = new BluetoothLEAdvertisementWatcher();

            watcher.Received += OnAdvertisementReceived;
        }

        private async void OnAdvertisementReceived(BluetoothLEAdvertisementWatcher watcher, BluetoothLEAdvertisementReceivedEventArgs eventArgs)
        {
            var dev = await BluetoothLEDevice.FromBluetoothAddressAsync(eventArgs.BluetoothAddress);

            }


    }

In the line

var dev = await BluetoothLEDevice.FromBluetoothAddressAsync(eventArgs.BluetoothAddress)

it gives the error:

IAsyncOperation<Bluetooth> does not contain a definition for
'GetAwaiter' and the best extension method overload
'windowsRuntimeSystemExtensions.GetAwaiter(IAsyncAction)' requires a
receiver of type 'IAsyncAction'

I tried adding references to System.Runtime, System.Runtime.WindowsRuntime, and Windows but this error still appears.

From my searching, the reason seems to be that the method FromBluetoothAddressAsync should return a Task.

From "BluetoothLEDevice Class", I can check that FromBluetoothAddressAsync method has this signature:

public static IAsyncOperation<BluetoothLEDevice> FromBluetoothAddressAsync(
    UInt64 bluetoothAddress,
    BluetoothAddressType bluetoothAddressType
)

which means that it returns IAsyncOperation<BluetoothLEDevice>. The way I see it, this seems enough to be recognized as something as a Task<>.

Is the problem due to a broken link which allows IAsyncOperation<> to be recognized as a child of Task<>?

score 42 · Accepted Answer · edited Apr 20 '20 at 17:51

42

To await an IAsyncOperation, you need two things:

A reference to C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETCore\v4.5\System.Runtime.WindowsRuntime.dll
A reference to C:\Program Files (x86)\Windows Kits\10\UnionMetadata\Facade\Windows.WinMD

If either reference is missing then it won't work. You can also use the UwpDesktop nuget package, that will do the work for you.

Note: specifically GetAwaiter is extension in System namespace that is available from those references (you still need using System; - make sure you have not removed it from the file). The extension info is on MSDN - WindowsRuntimeSystemExtensions.GetAwaiter.

edited Apr 20 '20 at 17:51

Alexei Levenkov

98,904
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answered May 22 '17 at 00:12

Kevin Gosse

38,392
3
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1

thank you very much. 'UwpDesktop' solution worked for me.. now a different error pops up, but at least the await error doesn't show up. – kwagjj May 22 '17 at 09:29
1

I'm afraid that with build 15063 code never gets past the call to ```BluetoothLEDevice.FromBluetoothAddressAsync``` – abinop May 22 '17 at 22:06
The Another aswer is a real answer – György Gulyás Apr 07 '20 at 11:05
1

[System.Runtime.WindowsRuntime](https://www.nuget.org/packages/System.Runtime.WindowsRuntime/) nuget package worked in my end. – MAQ678 Feb 19 '21 at 12:47
1

System.Runtime.WindowsRuntime did the trick! Thanks – sanrnsam7 May 03 '21 at 05:53

score 22 · Answer 2 · answered Apr 26 '18 at 07:36

22

For some of the other UWP operations just add using System:

using System;

//...

// example - getting file reference:
var file = await Windows.Storage.ApplicationData.Current.LocalFolder.GetFileAsync("myFile.txt);

answered Apr 26 '18 at 07:36

Marek

1,688
1
29
47

score 1 · Answer 3 · answered Jun 11 '21 at 08:45

1

For a '.NET Standard 2.0' Library project, add these Nugets:

answered Jun 11 '21 at 08:45

juwens

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FromBluetoothAddressAsync IAsyncOperation does not contain a definition for 'GetAwaiter' error

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