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using System;
using System.Collections.Generic;
using System.Linq;
using Windows.System.Threading;
using Windows.UI.Xaml.Controls;
namespace VirtualizingSearchExample {
sealed partial class MainPage {
// This constant defines a type of control that can be shown in the search results
// (each item is represented in text and visually by a text block and slider, with a fixed layout height of 40)
// (the code to populate the controls is specified when adding items)
private static readonly FastVerticallyScrollingItemViewer.IVirtualControlType SliderTextControlType
= new FastVerticallyScrollingItemViewer.AnonymousVirtualControlType(
height: 40,
maker: () => {
var g = new StackPanel();
g.Children.Add(new TextBlock());
g.Children.Add(new Slider());
return g;
// the range of numbers to search over
private static readonly int SearchRangeMax = (int)Math.Pow(10, 5);
private static readonly IEnumerable<int> SearchRange =
Enumerable.Range(0, SearchRangeMax) // possible results
.Select(e => ((e + 5)*11)%SearchRangeMax); // make results arrive out of order
public MainPage() {
// an object to synchronize changes to the displayed search results
var searchSyncRoot = new object();
// initialize the fast viewer to get a controller/driver with a type matching the values we want to represent
var controller = fastView.Init<int>();
// This method changes the search results to match some new filter, discarding old results
var curSearchId = 0;
Action<string> updateSearch = filter => {
// clear and cancel previous search
int thisSearchId;
lock (searchSyncRoot) {
// end previous search
thisSearchId = ++curSearchId;
// clear previous results
// do the search NOT on the ui thread, so we don't lock it up
ThreadPool.RunAsync(x => {
// enumerate matching results, showing them as we go
foreach (var result in SearchRange.Where(i => i.ToString().Contains(filter))) {
lock (searchSyncRoot) {
// if a new search has started, we'd better stop adding results
if (curSearchId != thisSearchId) break;
// add a newly found result
// a key to identify the search result, used for more efficient caching
key: result,
// the virtual control used to show the search result
value: new FastVerticallyScrollingItemViewer.AnonymousVirtualControlValue(
// the control type our value is represented by
virtualControlType: SliderTextControlType,
// how to fill in the given control type with our value
filler: control => {
var stackPanel = (StackPanel)control;
var textBlock = (TextBlock)stackPanel.Children.First();
var slider = (Slider)stackPanel.Children.Last();
textBlock.Text = "" + result;
slider.Value = result/(double)SearchRangeMax*100;
// how to adjust the given given control type as our value changes
updateContentsIn: xx => { }));
// wire-up searching to the text entered by the user
txtSearch.Text = "123";
txtSearch.TextChanged += (sender, arg) => updateSearch(txtSearch.Text);