ReactiveUI "Compelling Example" how to refresh the search results - wpf

Question

My question is in regards to the "Compelling Example" given for ReactiveUI where as a person types in a search bar, the search occurs asynchronously. Suppose though I wanted to provide my user with a way to refresh the current search results. I could just ask them to backspace in the search bar and retype their last character. However, they are asking for a "Refresh" button because it's not obvious to them how to refresh the current results.
I can't think of how to do this within the context of the example:
public class TheViewModel : ReactiveObject
{
private string query;
private readonly ObservableAsPropertyHelper<List<string>> matches;
public TheViewModel()
{
var searchEngine = this.ObservableForProperty(input => input.Query)
.Value()
.DistinctUntilChanged()
.Throttle(TimeSpan.FromMilliseconds(800))
.Where(query => !string.IsNullOrWhiteSpace(query) && query.Length > 1);
var search = searchEngine.SelectMany(TheSearchService.DoSearchAsync);
var latestResults =
searchEngine.CombineLatest(search, (latestQuery, latestSearch) => latestSearch.Query != latestQuery ? null : latestSearch.Matches)
.Where(result => result != null);
matches = latestResults.ToProperty(this, result => result.Matches);
}
public string Query
{
get
{
return query;
}
set
{
this.RaiseAndSetIfChanged(ref query, value);
}
}
public List<string> Matches
{
get
{
return matches.Value;
}
}
}
Does anyone have any suggestions on how I could capture a command from a button and re-execute the existing search without clearing out their current search text?

Answer 1

You can merge the existing observable of Query changes with a new observable that returns the current Query when the refresh button is pressed.
First a command for the refresh button:
public ReactiveCommand<Unit, String> Refresh { get; private set; }
Then you create the command and assign it, and create a merged observable of the two observables:
Refresh = ReactiveCommand.Create<Unit, String>(() => Query);
var searchEngine = Observable.Merge(
this.ObservableForProperty(input => input.Query).Value().DistinctUntilChanged(),
Refresh)
.Throttle(TimeSpan.FromMilliseconds(800))
.Where(query => !string.IsNullOrWhiteSpace(query) && query.Length > 1);
The rest can stay unchanged.