private IBluetoothProfileServiceListener _bluetoothProfileServiceListener;

public BluetoothAdapter MBluetoothAdapter;

MBluetoothAdapter = BluetoothAdapter.DefaultAdapter;
_bluetoothProfileServiceListener = new ServiceListener();
MBluetoothAdapter.GetProfileProxy(BaseContext,
_bluetoothProfileServiceListener, ProfileType.A2dp);

private class ServiceListener : IBluetoothProfileServiceListener
    {
        public void Dispose()
        {

        }

        public IntPtr Handle { get; }
public void OnServiceConnected(ProfileType profile,IBluetoothProfile proxy)
        {
            if (profile == ProfileType.A2dp)
            {
                //service connected
            }

        }

        public void OnServiceDisconnected(ProfileType profile)
        {

        }
    }