Got CS4036 error 'IAsyncOperation<BluetoothLEDevice>' does not contain a definition for 'GetAwaiter' ....

Question

Hello,
I am getting this error but I do not know how to recover it.

Error CS4036 'IAsyncOperation<BluetoothLEDevice>' does not contain a definition for 'GetAwaiter' and no extension method 'GetAwaiter' accepting a first argument of type 'IAsyncOperation<BluetoothLEDevice>' could be found (are you missing a using directive for 'System'?)

the code is

using System;  
using System.IO;  
using System.Collections;  
using System.Collections.Generic;  
using System.Data;  
using System.Data.SqlClient;  
using System.Runtime.InteropServices.WindowsRuntime;  
using System.Text;  
using System.Threading;  
using System.Threading.Tasks;  
using Windows.Devices.Enumeration.Pnp;  
using Windows.Foundation;  
using Windows.Devices.Bluetooth;  
using Windows.Devices.Bluetooth.GenericAttributeProfile;  
using Windows.Devices.Enumeration;  
using Windows.Storage.Streams;  
  
......  
static BluetoothLEDevice device;  
static DeviceWatcher watcher;  
static string deviceName;  
........  
async static void DeviceAdded(DeviceWatcher sender, DeviceInformation deviceInfo)  
{  
    // If the random device matches our device name, connect to it.  
    //Console.WriteLine("Device found: " + deviceInfo.Name);  
    if (deviceInfo.Name.CompareTo(deviceName) == 0)  
    {  
        // Get the bluetooth object and save it. This function will connect to the device  
       device = await BluetoothLEDevice.FromIdAsync(deviceInfo.Id);  
        Console.WriteLine("Connected to " + device.Name);  

        isDeviceConnected = true;  
    }  
}  

  

and the error is got at the line 13 "device = await ..... "

There are other points in the code with similar code with GattService or GattCharacteristic or .WriteValueWithResultAsync which are getting the same error.

The code I posted is a void routine, all the others are Task.

What do I have to do to correct my code?

Thanks a lot
Maurizio

Answer 1

@Maurizio Bonelli , Welcome to Microsoft Q&A, based on my research, I could solve the above error.

First, please install Nuget-Package System.Runtime.WindowsRuntime.

Second, please add Windows.winmd from the following path:

C:\Program Files (x86)\Windows Kits\10\UnionMetadata\10.0.19041.0  

Like the following:

Third, please rebuild your project and you will see the project is built successfully.

Hope my solution could help you.

Best Regards,
Jack

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Answer 2

Have you added a reference to System.Runtime.WindowsRuntime.dll ?
(you can see threads like Call WinRT API from Desktop App (On Windows 10)

Answer 3

@Castorix31

Thanks for reply, but it appears I do not have that System.Runtime.WindowsRuntime.dll in my system, neither in .NETFramwork/4.8 (which is the one I am using for this code) nor in any others.
In the ..../NET/4.5 there is a System.Runtime.WindowsRuntime.xml but I do not think it is the same, also because I am using .NETFramework.

The code is an example got from https://github.com/SiliconLabs/bluetooth_stack_features/blob/master/firmware_upgrade/bluetooth_ota_from_windows/src/Program.cs
and I will modify for my needing after it will work.... and I am not so skilled in async methods....

thanks again
Maurizio