Reactive Extensions Instant Search for WPF/MVVM

Question

I would like to implement a TextBox where, as you type, results appear instantly in another ListBox. I\'ve been looking for examples with Reactive Extensions (Rx), and all o

Answer 1

Got this working with ReactiveUI.

The solution is based on a blog post at ReactiveUI, but the code there is a little bit out of date. I am hosting the solution on BitBucket for ease of access. It uses ReactiveUI 5.5.1.

This is the ViewModel from that solution. SearchText is bound to a TextBox in the View where the user types his query, while SearchResults is bound to a ListBox displaying the results.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections.ObjectModel;
using System.Threading.Tasks;
using System.ComponentModel;
using System.Reactive.Linq;
using System.Windows.Input;

using ReactiveUI;

namespace ReactiveExtensionsSearch
{
    public class MainWindowViewModel : ReactiveObject
    {
        private string[] _repository = new string[]
            { "Mario", "Maria", "Gigi", "Jack", "James", "Jeremy" };
        private ObservableAsPropertyHelper> _searchResults;
        private string _searchText;
        private ICommand _executeSearchCommand;

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

        public ObservableCollection SearchResults
        {
            get
            {
                return _searchResults.Value;
            }
        }

        public MainWindowViewModel()
        {
            var executeSearchCommand = new ReactiveCommand();
            var results = executeSearchCommand.RegisterAsyncFunction(s => { return ExecuteSearch(s as string); });
            _executeSearchCommand = executeSearchCommand;

            this.ObservableForProperty("SearchText")
                .Throttle(TimeSpan.FromMilliseconds(800))
                .Select(x => x.Value)
                .DistinctUntilChanged()
                .Where(x => !string.IsNullOrWhiteSpace(x))
                .Subscribe(_executeSearchCommand.Execute);

           _searchResults = new ObservableAsPropertyHelper>(results, _ => raisePropertyChanged("SearchResults"));
        }

        private ObservableCollection ExecuteSearch(string searchText)
        {
            var q = from s in _repository where s.ToLower().StartsWith(searchText.ToLower()) select s;
            var results = new ObservableCollection(q);
            return results;
        }
    }
}