Example of Bluetooth in Xamarin.Forms applications - http://julianocustodio.com/bluetooth

MainPageSearchDevice.cs

...

private async void searchDevice(object sender, EventArgs e)
        {
            if (bluetoothBLE.State == BluetoothState.Off)
            {
                await DisplayAlert("Atenção", "Bluetooth desabilitado.", "OK");
            }
            else
            {
                list.Clear();

                adapter.ScanTimeout = 10000;
                adapter.ScanMode = ScanMode.Balanced;


                adapter.DeviceDiscovered += (obj, a) =>
                {
                    if (!list.Contains(a.Device))
                        list.Add(a.Device);
                };

                await adapter.StartScanningForDevicesAsync();
                
            }

        }
        
...