public TwitterSearchModel(string searchTerm)
 {
     Since = "1";
     SearchTerm = searchTerm;
     Tweets = new BindableObservableCollection<Tweet>();
     Update();
 }
        public TwitterSearchesViewModel(CoreDispatcher dispatcher)
        {
            _dispatcher = dispatcher;
            Searches = new BindableObservableCollection<TwitterSearchViewModel>();

            this.SearchCommand = new SearchCommand(this);
            this.RefreshCommand = new RefreshCommand(this);
        }