sample.cs

//...

var currentContext = Android.App.Application.Context;
var receiver = new BluetoothDeviceDiscoverReceiver(currentContext);

var filter = new IntentFilter(BluetoothDevice.ActionFound);
filter.AddAction(BluetoothAdapter.ActionDiscoveryStarted);
filter.AddAction(BluetoothAdapter.ActionDiscoveryFinished);

currentContext.RegisterReceiver(receiver, filter);

bluetoothAdapter.StartDiscovery();


//...