Autocomplete combobox for WPF

Question

I need an autocomplete combobox for WPF C#. I\'ve tried several approaches but nothing works. For example I\'ve tried a combobox:

Answer 1

Here is the implementation that works for me:

I check if the text has changed since the last time the filter was applied (to avoid filtering when a non-alphanumeric key is pressed).

private string _textBeforeFilter;

private void OnItemsControlKeyUp(object sender, KeyEventArgs e)
{
    var arrowKey = e.Key >= Key.Left && e.Key <= Key.Down;

    // if arrow key (navigating) or the text hasn't changed, then a we don't need to filter
    if (arrowKey || ItemsControl.Text.EqualsIgnoreCase(_textBeforeFilter)) return;

    _textBeforeFilter = ItemsControl.Text;

    var textIsEmpty = string.IsNullOrWhiteSpace(ItemsControl.Text);

    var itemsViewOriginal = (CollectionView) CollectionViewSource.GetDefaultView(ItemsControl.ItemsSource);
    // if the text is empty, then we show everything, otherwise filter based on the text 
    itemsViewOriginal.Filter = o => textIsEmpty || ((string) o).ContainsIgnoreCase(ItemsControl.Text);
}

NOTE: EqualsIgnoreCase and ContainsIgnoreCase are extension methods:

public static bool EqualsIgnoreCase(this string source, string value)
{
    return source.Equals(value, StringComparison.OrdinalIgnoreCase);
}

public static bool ContainsIgnoreCase(this string source, string value)
{
    return source.Contains(value, StringComparison.OrdinalIgnoreCase);
}