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nitish.mohiputlall -4 Junior Poster in Training

what are the codes to use to filter out my listbox as the user is typing in the textbox?

the data in my listbox is from database. I have used a relay command to get all the details of an Event then place the details in an observable collection. Then bind my listbox to the observable collection and a textblock to show the Event Names.

xaml codes:

<TextBox  x:Name="txtSearch" Background="White" FontSize="30"  Height="57" Margin="19,10,19,0" Grid.Row="1" />
<Grid Grid.Row="1" x:Name="ContentRoot" Margin="19,72,19,0">
        <ListBox Background="Black"  x:Name="listBox" FontSize="26" Margin="0,10,0,0" LayoutUpdated="listbox_layoutUpdate" ItemsSource="{Binding HomePage.SearchEventCollection}">
            <ListBox.ItemTemplate >
                <DataTemplate>
                    <StackPanel Orientation="Horizontal">
                        <TextBlock x:Name="txtEventName" TextWrapping="Wrap" Text="{Binding EventName}" Tapped="txtEventName_Tapped" IsTapEnabled="True" Foreground="White" Width="300" Margin="10,15,0,0" Height="55"/>
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </Grid>



relay command in viewmodel:

private RelayCommand _eventSearch;

    /// <summary>
    /// Gets the EventSearch.
    /// </summary>
    public RelayCommand EventSearch
    {
        get
        {
            return _eventSearch
                ?? (_eventSearch = new RelayCommand(
                async() =>
                {
                    SearchEventCollection.Clear();
                    var eventList = await App.MobileService.GetTable<Event>().ToListAsync();

                    foreach (Event ename in eventList)
                    {
                        SearchEventCollection.Add(new Event
                        {
                            Id = ename.Id,
                            EventName = ename.EventName,
                            Date = ename.Date,
                            Location = ename.Location,
                            Desc = ename.Desc
                        });
                    }
                }));
        }
    }

    }



private static ObservableCollection<Event> _searchEventCollection = new ObservableCollection<Event>();

    public static ObservableCollection<Event> SearchEventCollection
    {
        get { return _searchEventCollection; }
        set { _searchEventCollection = value; }
    }
  • 1 Contributor
  • 0 Replies
  • 183 Views

Dani AI

Generated

A simple, reliable pattern is to keep a master collection of all events and expose a second, filtered ObservableCollection that the ListBox binds to. Populate the master list once (your existing RelayCommand can do that), then update the filtered collection whenever the search text changes. This avoids destructive filtering and keeps UI updates easy to control from the ViewModel.

Example ViewModel sketch (MVVM Light helpers used for UI dispatching and property notifications):

private ObservableCollection<Event> _allEvents = new ObservableCollection<Event>();
private ObservableCollection<Event> _filteredEvents = new ObservableCollection<Event>();
public ObservableCollection<Event> FilteredEvents => _filteredEvents;

private string _query;
public string Query {
  get => _query;
  set {
    if (_query == value) return;
    _query = value;
    RaisePropertyChanged("Query");
    DebounceFilter();
  }
}

private CancellationTokenSource _debounceCts;
private async void DebounceFilter() {
  _debounceCts?.Cancel();
  _debounceCts = new CancellationTokenSource();
  try {
    await Task.Delay(300, _debounceCts.Token); // 300ms debounce
  } catch (TaskCanceledException) { return; }
  ApplyFilter();
}

private void ApplyFilter() {
  var q = string.IsNullOrWhiteSpace(_query) ? null : _query.Trim().ToLowerInvariant();
  var matches = string.IsNullOrEmpty(q) ? _allEvents : _allEvents.Where(e => (e.EventName ?? "").ToLowerInvariant().Contains(q));
  DispatcherHelper.CheckBeginInvokeOnUI(() => {
    _filteredEvents.Clear();
    foreach (var e in matches) _filteredEvents.Add(e);
  });
}

Minimal XAML (bind the TextBox to Query and the ListBox to FilteredEvents):

<TextBox Text="{Binding Query, Mode=TwoWay}" />
<ListBox ItemsSource="{Binding FilteredEvents}" />

Notes: call DispatcherHelper.Initialize() from App startup so DispatcherHelper works. For small lists this in-memory filter is fine; for large datasets prefer server-side filtering (send the query and fetch matches). Tie this into your existing data load by filling _allEvents in the command that currently fetches rows, then call ApplyFilter() once to populate FilteredEvents. This keeps typing responsive and predictable for users.

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