MainPageViewModel.cs

namespace DynamicDataGroupingSample
{
    public class MainViewModel : ReactiveObject, IDisposable
    {
        public MainViewModel()
        {
            // Initial data
            _sourceCache.AddOrUpdate(new List<Restaurant>()
            {
                new Restaurant("Yao","Casual","Asian Fusion","Dominican Republic"),
                new Restaurant("Chef Pepper","Casual","International","Dominican Republic"),
                new Restaurant("Bottega Fratelli","Formal","International","Dominican Republic"),
                new Restaurant("McDonalds","Fast Food","Burgers","United States"),
                new Restaurant("Burger King","Fast Food","Burgers","United States"),
                new Restaurant("Sushi Nation","Casual","Sushi","Venezuela"),
                new Restaurant("Pollo Victorina","Fast Food","Chicken","Dominican Republic"),
                new Restaurant("Pollo Rey","Fast Food","Chicken","Dominican Republic"),
                new Restaurant("Asadero Argetino","Formal","Meat","Dominican Republic"),
                new Restaurant("Hooters","Casual","Wings","United States"),
                new Restaurant("Andres Carne","Casual","Meat","Colombia"),
                new Restaurant("La Casita","Casual","Colombian Food","Colombia"),
                new Restaurant("Cielo","Formal","International","Colombia"),
            });

            //Search logic
            Func<Restaurant, bool> restaurantFilter(string text) => restaurant =>
            {
                return string.IsNullOrEmpty(text) || restaurant.Name.ToLower().Contains(text.ToLower()) || restaurant.Type.ToLower().Contains(text.ToLower());
            };

            var filterPredicate = this.WhenAnyValue(x => x.SearchText)
                                      .Throttle(TimeSpan.FromMilliseconds(250), RxApp.TaskpoolScheduler)
                                      .DistinctUntilChanged()
                                      .Select(restaurantFilter);

            _cleanUp = _sourceCache.Connect()
            .RefCount()
            .Filter(filterPredicate)
            .Sort(sortPredicate)
            .Bind(out _restaurants)
            .DisposeMany()
            .Subscribe();
        }     

        public void Dispose()
        {
            _cleanUp.Dispose();
        }

        public ReadOnlyObservableCollection<Restaurant> Restaurants => _restaurants;

        public string SearchText
        {
            get => _searchText;
            set => this.RaiseAndSetIfChanged(ref _searchText, value);
        }

        private SourceCache<Restaurant, string> _sourceCache = new SourceCache<Restaurant, string>(x => x.Id);
        private readonly ReadOnlyObservableCollection<Restaurant> _restaurants;
        private string _searchText;

        private readonly IDisposable _cleanUp;
    }
}