await can't find GetAwaitor method

__John_

The error...

Error 1 'await' requires that the type 'Windows.Foundation.IAsyncOperation' have a suitable GetAwaiter method. Are you missing a using directive for 'System'? C:\Users\jo\Documents\Visual Studio 2013\Projects\Btle01\Btle01\Form1.cs 29 46 Btle01

My code...

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Text;
using System.Windows.Forms;
using System.Threading;
using System.Threading.Tasks;
using Windows.Devices.Bluetooth;
using Windows.Devices.Enumeration;
using Windows.Foundation;
using Windows.System;

namespace Btle01
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

    private void OnFormLoad(object sender, EventArgs e)
    {
    }

    private async Task GetDevs()
    {
        foreach (DeviceInformation di in await Windows.Devices.Enumeration.DeviceInformation.FindAllAsync(BluetoothLEDevice.GetDeviceSelector()))
        {
            BluetoothLEDevice bleDevice = await BluetoothLEDevice.FromIdAsync(di.Id);
            listView1.Items.Add(bleDevice.Name);
        }
    }

}

}

List of project references...

False
..\..\..\..\..\..\..\Windows\Microsoft.NET\Framework64\v4.0.30319\System.Runtime.WindowsRuntime.dll

..\\..\\..\\..\\..\\..\\..\\Windows\\System32\\WinMetadata\\Windows.Devices.winmd

Nathan Minier

I see that this has been gathering dust for a few days, so I'm sorry if I'm too late to the party to help you.

foreach (DeviceInformation di in await Windows.Devices.Enumeration.DeviceInformation.FindAllAsync(BluetoothLEDevice.GetDeviceSelector()))

This is a problem. basically you're attempting to iterate a collection of promises, but without a custom iterator the compiler has no idea what to do with those promises. The easy fix is to move the asynch resolution to a variable and await it, like so:

...
// allow synchronization before iteration
var myArray = await Windows.Devices.Enumeration.DeviceInformation.FindAllAsync(BluetoothLEDevice.GetDeviceSelector());

foreach(DeviceInformation di in myArray)
...

Alternatively, you can abuse some of the async functionality in LINQ (I haven't validated this block, so it might need tweaking):

var result = await Task.WhenAll(Windows.Devices.Enumeration.DeviceInformation
.FindAllAsync(BluetoothLEDevice.GetDeviceSelector())
.Select(async x => await BluetoothLEDevice.FromIdAsync(x.Id)).ToArray());

result.Select(x => listView1.Items.Add(x.Name));

There are plenty of other ways to skin this cat, should you happen to like cat skins. Both of these approaches should work, though.

__John_

Hi Nathan, thanks for the response, I will try your suggestions. - John

“If I had asked people what they wanted, they would have said faster horses.” ― Henry Ford