public class FilteredComboBox : ComboBox
{
/// <summary>
/// If true, on lost focus or enter key pressed, checks the text in the combobox. If the text is not present
/// in the list, it leaves it blank.
/// </summary>
public bool OnlyValuesInList
{
get => (bool)GetValue(OnlyValuesInListProperty);
set => SetValue(OnlyValuesInListProperty, value);
}
public static readonly DependencyProperty OnlyValuesInListProperty =
DependencyProperty.Register(nameof(OnlyValuesInList), typeof(bool), typeof(FilteredComboBox));
/// <summary>
/// Selected item, changes only on lost focus or enter key pressed
/// </summary>
public object EffectivelySelectedItem
{
get => (bool)GetValue(EffectivelySelectedItemProperty);
set => SetValue(EffectivelySelectedItemProperty, value);
}
public static readonly DependencyProperty EffectivelySelectedItemProperty =
DependencyProperty.Register(nameof(EffectivelySelectedItem), typeof(object), typeof(FilteredComboBox));
private string CurrentFilter = string.Empty;
private bool TextBoxFreezed;
protected TextBox EditableTextBox => GetTemplateChild("PART_EditableTextBox") as TextBox;
private UserChange<bool> IsDropDownOpenUC;
/// <summary>
/// Triggers on lost focus or enter key pressed, if the selected item changed since the last time focus was lost or enter was pressed.
/// </summary>
public event Action<FilteredComboBox, object> SelectionEffectivelyChanged;
public FilteredComboBox()
{
IsDropDownOpenUC = new UserChange<bool>(v => IsDropDownOpen = v);
DropDownOpened += FilteredComboBox_DropDownOpened;
IsEditable = true;
IsTextSearchEnabled = true;
StaysOpenOnEdit = true;
IsReadOnly = false;
Loaded += (s, e) => {
if (EditableTextBox != null)
new TextBoxBaseUserChangeTracker(EditableTextBox).UserTextChanged += FilteredComboBox_UserTextChange;
};
SelectionChanged += (_, __) => shouldTriggerSelectedItemChanged = true;
SelectionEffectivelyChanged += (_, o) => EffectivelySelectedItem = o;
}
protected override void OnPreviewKeyDown(KeyEventArgs e)
{
base.OnPreviewKeyDown(e);
if (e.Key == Key.Down && !IsDropDownOpen)
{
IsDropDownOpen = true;
e.Handled = true;
}
else if (e.Key == Key.Escape)
{
ClearFilter();
Text = "";
IsDropDownOpen = true;
}
else if (e.Key == Key.Back)
{
ClearFilter();
Text = "";
IsDropDownOpen = true;
}
else if (e.Key == Key.Enter || e.Key == Key.Tab)
{
CheckSelectedItem();
TriggerSelectedItemChanged();
IsDropDownOpen = false;
}
}
protected override void OnPreviewLostKeyboardFocus(KeyboardFocusChangedEventArgs e)
{
base.OnPreviewLostKeyboardFocus(e);
CheckSelectedItem();
if ((e.OldFocus == this || e.OldFocus == EditableTextBox) && e.NewFocus != this && e.NewFocus != EditableTextBox)
TriggerSelectedItemChanged();
}
private void CheckSelectedItem()
{
if (OnlyValuesInList)
Text = SelectedItem?.ToString() ?? "";
}
private bool shouldTriggerSelectedItemChanged = false;
private void TriggerSelectedItemChanged()
{
if (shouldTriggerSelectedItemChanged)
{
SelectionEffectivelyChanged?.Invoke(this, SelectedItem);
shouldTriggerSelectedItemChanged = false;
}
}
public void ClearFilter()
{
if (string.IsNullOrEmpty(CurrentFilter)) return;
CurrentFilter = "";
CollectionViewSource.GetDefaultView(ItemsSource).Refresh();
}
private void FilteredComboBox_DropDownOpened(object sender, EventArgs e)
{
if (IsDropDownOpenUC.IsUserChange)
ClearFilter();
}
private void FilteredComboBox_UserTextChange(object sender, EventArgs e)
{
if (TextBoxFreezed) return;
var tb = EditableTextBox;
if (tb.SelectionStart + tb.SelectionLength == tb.Text.Length)
CurrentFilter = tb.Text.Substring(0, tb.SelectionStart).ToLower();
else
CurrentFilter = tb.Text.ToLower();
RefreshFilter();
}
protected override void OnItemsSourceChanged(IEnumerable oldValue, IEnumerable newValue)
{
if (newValue != null)
{
var view = CollectionViewSource.GetDefaultView(newValue);
view.Filter += FilterItem;
}
if (oldValue != null)
{
var view = CollectionViewSource.GetDefaultView(oldValue);
if (view != null) view.Filter -= FilterItem;
}
base.OnItemsSourceChanged(oldValue, newValue);
}
private void RefreshFilter()
{
if (ItemsSource == null) return;
var view = CollectionViewSource.GetDefaultView(ItemsSource);
FreezTextBoxState(() => {
var isDropDownOpen = IsDropDownOpen;
//always hide because showing it enables the user to pick with up and down keys, otherwise it's not working because of the glitch in view.Refresh()
IsDropDownOpenUC.Set(false);
view.Refresh();
if (!string.IsNullOrEmpty(CurrentFilter) || isDropDownOpen)
IsDropDownOpenUC.Set(true);
if (SelectedItem == null)
{
foreach (var itm in ItemsSource)
if (itm.ToString() == Text)
{
SelectedItem = itm;
break;
}
}
});
}
private void FreezTextBoxState(Action action)
{
TextBoxFreezed = true;
var tb = EditableTextBox;
var text = Text;
var selStart = tb.SelectionStart;
var selLen = tb.SelectionLength;
action();
Text = text;
tb.SelectionStart = selStart;
tb.SelectionLength = selLen;
TextBoxFreezed = false;
}
private bool FilterItem(object value)
{
var _newVal = ((NewComboSearch.MainWindow.ComboData)value).text;
if (_newVal == null) return false;
if (CurrentFilter.Length == 0) return true;
return _newVal.ToString().ToLower().Contains(CurrentFilter);
}
private class TextBoxBaseUserChangeTracker
{
private bool IsTextInput { get; set; }
public TextBoxBase TextBoxBase { get; set; }
private List<Key> PressedKeys = new List<Key>();
public event EventHandler UserTextChanged;
private string LastText;
public TextBoxBaseUserChangeTracker(TextBoxBase textBoxBase)
{
TextBoxBase = textBoxBase;
LastText = TextBoxBase.ToString();
textBoxBase.PreviewTextInput += (s, e) => {
IsTextInput = true;
};
textBoxBase.TextChanged += (s, e) => {
var isUserChange = PressedKeys.Count > 0 || IsTextInput || LastText == TextBoxBase.ToString();
IsTextInput = false;
LastText = TextBoxBase.ToString();
if (isUserChange)
UserTextChanged?.Invoke(this, e);
};
textBoxBase.PreviewKeyDown += (s, e) => {
switch (e.Key)
{
case Key.Back:
case Key.Space:
if (!PressedKeys.Contains(e.Key))
PressedKeys.Add(e.Key);
break;
}
if (e.Key == Key.Back)
{
var textBox = textBoxBase as TextBox;
if (textBox.SelectionStart > 0 && textBox.SelectionLength > 0 && (textBox.SelectionStart + textBox.SelectionLength) == textBox.Text.Length)
{
textBox.SelectionStart--;
textBox.SelectionLength++;
e.Handled = true;
UserTextChanged?.Invoke(this, e);
}
}
};
textBoxBase.PreviewKeyUp += (s, e) => {
if (PressedKeys.Contains(e.Key))
PressedKeys.Remove(e.Key);
};
textBoxBase.LostFocus += (s, e) => {
PressedKeys.Clear();
IsTextInput = false;
};
}
}
private class UserChange<T>
{
private Action<T> action;
public bool IsUserChange { get; private set; } = true;
public UserChange(Action<T> action)
{
this.action = action;
}
public void Set(T val)
{
try
{
IsUserChange = false;
action(val);
}
finally
{
IsUserChange = true;
}
}
}
}
