Error loading custom DLL with async for BLE

Hello! This is my first post here and first time developing with Unity so I would appreciate a walk through.

I'm trying to add BLE functionality to an existing Windows 10 Unity app. I'm using a BLE dongle to interface with a hardware device (custom designed and programmed board). I created a Visual Studio C# (.NET framework) project which uses Windows.Devices.Bluetooth (and therefore needs Windows.winmd). I couldn't get Unity to import Windows.winmd so I made a DLL with the functionality.

This DLL loads Windows.Devices.Bluetooth and uses async/await calls. Mainly this: // Function to connect to device with given address: addr private async void ConnectAndStartReading(ulong addr, string s_uuid, string c_uuid) { // Connect to device device = await BluetoothLEDevice.FromBluetoothAddressAsync(addr);

             // Get service async
             GattDeviceServicesResult s = await device.GetGattServicesForUuidAsync(Guid.Parse(s_uuid));
             service = s.Services[0];
 
             // Get characteristic async
             GattCharacteristicsResult c = await service.GetCharacteristicsForUuidAsync(Guid.Parse(c_uuid));
             characteristic = c.Characteristics[0];
 
             // Set config description value to notify
             GattCommunicationStatus status = await characteristic.WriteClientCharacteristicConfigurationDescriptorAsync(GattClientCharacteristicConfigurationDescriptorValue.Notify);
 
             // Set characteristic value change callback
             characteristic.ValueChanged += Handler_CharacteristicValueChanged;
         }

In the Handler_CharacteristicValueChanged function, it sets 3 variables (roll, pitch and yaw) from the buffer. I'd like the Unity program to read the 3 public variables.

Again, this works fine on a non-Unity app. (Here are some snippets)

 namespace ARC_BLE_Interface_Test
 {
     class Program
     {
         public static BLE_Interface ble;
 
         static void Main(string[] args)
         {
             // Device specifications
             ulong dev_addr = 255782611406774;
 
             // Service UUID
             string data_stream_service_uuid = "0000fe84-0000-1000-8000-00805f9b34fb";
 
             // Characteristic UUID
             string data_stream_char_uuid = "2d30c082-f39f-4ce6-923f-3484ea480596";
 
             ble = new BLE_Interface(dev_addr, data_stream_service_uuid, data_stream_char_uuid);
 
             while (true)
             {
                 Console.WriteLine(ble.roll + "\t" + ble.pitch + "\t" + ble.yaw);
 
                 Thread.Sleep(50);
             }
         }
     }
 }

but not with Unity. I have an implementation like this:

 public BLE_Interface ble;
 
     void Start()
     {
         ble = new BLE_Interface(device_address, data_stream_service_uuid, data_stream_char_uuid);
     }
 
     void Update()
     {
         ConsoleController.HotMessage(ble.roll.ToString());
     }

I get the following errors: TypeLoadException: Could not find method due to a type load error Unloading broken assembly Assets/dll/ARC_BLE_Interface.dll, this assembly can cause crashes in the runtime

Any ideas?

Thank you very much! Let me know if you need any more information. I haven't really programmed in C# or Unity before yesterday.

Cheers!