1912UWPBLE_2.cs

private async void OnAdvertisementReceived(BluetoothLEAdvertisementWatcher watcher, 
BluetoothLEAdvertisementReceivedEventArgs eventArgs)
{
    //アドバタイズ受信した際の処理
    await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
    {
        //同要素がなければListに追加
        AdvertisementListItem item = new AdvertisementListItem(eventArgs);
        if (AdvertisementList.Select(x => x.BluetoothAddress).Where(x => x.Equals(item.BluetoothAddress)).Count() == 0)
        {
            AdvertisementList.Add(item);
        }
   });
}