CentralizedControl/HandyControl/HandyControl_Shared/Controls/Input/AutoCompleteTextBox/AutoCompleteTextBox.cs

using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using HandyControl.Data;
using HandyControl.Tools.Helper;

namespace HandyControl.Controls;

[TemplatePart(Name = SearchTextBox, Type = typeof(System.Windows.Controls.TextBox))]
public class AutoCompleteTextBox : ComboBox
{
    private const string SearchTextBox = "PART_SearchTextBox";

    private bool ignoreTextChanging;

    private System.Windows.Controls.TextBox _searchTextBox;

    private object _selectedItem;

    static AutoCompleteTextBox()
    {
        TextProperty.OverrideMetadata(typeof(AutoCompleteTextBox), new FrameworkPropertyMetadata(default(string), FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));
    }

    public override void OnApplyTemplate()
    {
        if (_searchTextBox != null)
        {
            _searchTextBox.GotFocus -= SearchTextBoxGotFocus;
            _searchTextBox.KeyDown -= SearchTextBoxKeyDown;
            _searchTextBox.TextChanged -= SearchTextBoxTextChanged;
        }

        base.OnApplyTemplate();

        _searchTextBox = GetTemplateChild(SearchTextBox) as System.Windows.Controls.TextBox;
        if (_searchTextBox != null)
        {
            _searchTextBox.GotFocus += SearchTextBoxGotFocus;
            _searchTextBox.PreviewKeyDown += SearchTextBoxKeyDown;
            _searchTextBox.TextChanged += SearchTextBoxTextChanged;
        }

        UpdateTextBoxBySelectedItem(_selectedItem);
    }

    protected override void OnSelectionChanged(SelectionChangedEventArgs e)
    {
        base.OnSelectionChanged(e);

        if (e.AddedItems.Count > 0)
        {
            _selectedItem = e.AddedItems[0];
            UpdateTextBoxBySelectedItem(_selectedItem);
        }
    }

    protected override bool IsItemItsOwnContainerOverride(object item) => item is AutoCompleteTextBoxItem;

    protected override DependencyObject GetContainerForItemOverride() => new AutoCompleteTextBoxItem();

    private void SearchTextBoxTextChanged(object sender, TextChangedEventArgs e)
    {
        _selectedItem = null;
        SelectedIndex = -1;

        if (ignoreTextChanging)
        {
            ignoreTextChanging = false;
            return;
        }

        Text = _searchTextBox.Text;
        if (string.IsNullOrEmpty(Text))
        {
            SetCurrentValue(IsDropDownOpenProperty, ValueBoxes.FalseBox);
            _searchTextBox.Focus();
        }
        else if (_searchTextBox.IsFocused)
        {
            SetCurrentValue(IsDropDownOpenProperty, ValueBoxes.TrueBox);
        }
    }

    private void SearchTextBoxKeyDown(object sender, KeyEventArgs e)
    {
        if (e.Key == Key.Up)
        {
            var index = SelectedIndex - 1;
            if (index < 0)
            {
                index = Items.Count - 1;
            }

            UpdateTextBoxBySelectedIndex(index);
        }
        else if (e.Key == Key.Down)
        {
            var index = SelectedIndex + 1;
            if (index >= Items.Count)
            {
                index = 0;
            }

            UpdateTextBoxBySelectedIndex(index);
        }
        else if (e.Key == Key.Enter)
        {
            SetCurrentValue(IsDropDownOpenProperty, ValueBoxes.FalseBox);
            e.Handled = true;
        }
    }

    private void UpdateTextBoxBySelectedIndex(int selectedIndex)
    {
        if (_searchTextBox == null)
        {
            return;
        }

        ignoreTextChanging = true;

        if (ItemContainerGenerator.ContainerFromIndex(selectedIndex) is AutoCompleteTextBoxItem boxItem)
        {
            _searchTextBox.Text = BindingHelper.GetString(boxItem.Content, DisplayMemberPath);
            _searchTextBox.CaretIndex = _searchTextBox.Text.Length;

            SelectedIndex = selectedIndex;
        }
    }

    private void UpdateTextBoxBySelectedItem(object selectedItem)
    {
        if (_searchTextBox == null)
        {
            return;
        }

        ignoreTextChanging = true;

        _searchTextBox.Text = BindingHelper.GetString(selectedItem, DisplayMemberPath);
        _searchTextBox.CaretIndex = _searchTextBox.Text.Length;

        ignoreTextChanging = true;

        Text = _searchTextBox.Text;

        ignoreTextChanging = false;
    }

    private void SearchTextBoxGotFocus(object sender, RoutedEventArgs e)
    {
        if (!string.IsNullOrEmpty(Text))
        {
            SetCurrentValue(IsDropDownOpenProperty, ValueBoxes.TrueBox);
        }
    }
}