This simple WPF demo with ReactiveUI
I have added a file search which searches for files in the local My Pictures folder of the user. If you want to replace the Flickr photo search from the original example with the local file search just replace the following line in AppViewModel.cs:
var ExecuteSearch = ReactiveCommand.CreateFromTask((string searchedTerm) => FlickrPhotoSearch.Search(searchedTerm));with
var ExecuteSearch = ReactiveCommand.CreateFromTask((string searchedTerm) => MyPicturesSearch.Search(searchedTerm));