How to get list of Wifi Networks

I am trying to get a list of Wifi Networks. I am trying to isolate the code into its own class (see below.) The Intent Filter WifiReceiver never seems to be called. Once it is working, since I don't necessarily know when the WiFiNetworks List will be completely populated, is it proper programming, in Android, to set a flag letting me know once the WifiReciever class has completed populating the List? I want to populate a Spinner with the results from this List.

using Android.Content;
using Android.Net.Wifi;
using System.Collections.Generic;
using System.Text;
using System.Threading;
namespace RingerLocation.Utility
{
    public class Wifi
    {
        private Context context = null;
        private static WifiManager wifi;
        private WifiReceiver wifiReceiver;
        public static List<string> WiFiNetworks;

        public Wifi(Context ctx)
        {
            this.context = ctx;
        }

        public void GetWifiNetworks()
        {
            WiFiNetworks = new List<string>();

            // Get a handle to the Wifi
            wifi = (WifiManager)context.GetSystemService(Context.WifiService);

            // Start a scan and register the Broadcast receiver to get the list of Wifi Networks
            wifiReceiver = new WifiReceiver();
            context.RegisterReceiver(wifiReceiver, new IntentFilter(WifiManager.ScanResultsAvailableAction));
            wifi.StartScan();
        }

        class WifiReceiver : BroadcastReceiver
        {
            public override void OnReceive(Context context, Intent intent)
            {
                IList<ScanResult> scanwifinetworks = wifi.ScanResults;
                foreach(ScanResult wifinetwork in scanwifinetworks)
                {
                    WiFiNetworks.Add(wifinetwork.Ssid);
                }
            }
        }
    }
}