public void Start()
{
if (context == null)
{
throw new Exception("Context not set.");
}
if (_broadcastReceiver != null)
{
throw new InvalidOperationException(
"Network status monitoring already active.");
}
// Create the broadcast receiver and bind the event handler
// so that the app gets updates of the network connectivity status
_broadcastReceiver = new NetworkStatusBroadcastReceiver();
_broadcastReceiver.ConnectionStatusChanged += OnNetworkStatusChanged;
// Register the broadcast receiver
context.RegisterReceiver(_broadcastReceiver,
new IntentFilter(ConnectivityManager.ConnectivityAction));
}