WPF 如何自定义隐藏下拉框选项

<ComboBox  IsTextSearchEnabled="False"                        IsEditable="True"                      ItemsSource="source" <!--source {value：string， text：string }-->                      KeyUp="comboBox_KeyUp" DropDownOpened="OnDropDownOpened"   DropDownClosed="OnDropDownClosed"/>

/// <summary>/// 搜索条件过滤/// </summary> private void comboBox_KeyUp(object sender, System.Windows.Input.KeyEventArgs e) {         var combobox = (ComboBox)sender;        combobox.SelectedItem = null;        var ctb = combobox.Template.FindName("PART_EditableTextBox", combobox) as TextBox;        if (ctb == null) return;        if (Keyboard.Modifiers.HasFlag(ModifierKeys.Shift) || Keyboard.Modifiers.HasFlag(ModifierKeys.Control) || Keyboard.Modifiers.HasFlag(ModifierKeys.Alt))            return;        var caretPos = ctb.CaretIndex;        combobox.IsDropDownOpen = true;
        var datasource = (combobox.ItemsSource as List<SelectOption>).DeepClone().Where(x => /*自定义条件*/)).ToList();        combobox.ItemsSource = datasource;
        CollectionView itemsViewOriginal = (CollectionView)CollectionViewSource.GetDefaultView(combobox.Items);        itemsViewOriginal.Filter = ((o) =>        {            if (String.IsNullOrEmpty(combobox.Text))            {                return true;            }            else            {                if (((SelectOption)o).text.ToLower().Contains(combobox.Text.ToLower()))//(SelectOption)o).text.StartsWith(combobox.Text, true, null)                {                    return true;                }                else                {                    return false;                }            }        });
        itemsViewOriginal.Refresh();        ctb.CaretIndex = caretPos;    }    /// <summary>    /// 下拉框初始化过滤    /// </summary>  private void OnDropDownOpened(object sender, EventArgs e)    {        var cb = (ComboBox)sender;        if (cb.IsDropDownOpen == true)        {            var combobox = (ComboBox)sender;            //combobox.SelectedItem = null;            var ctb = combobox.Template.FindName("PART_EditableTextBox", combobox) as TextBox;            if (ctb == null) return;            if (Keyboard.Modifiers.HasFlag(ModifierKeys.Shift) || Keyboard.Modifiers.HasFlag(ModifierKeys.Control) || Keyboard.Modifiers.HasFlag(ModifierKeys.Alt))                return;            var caretPos = ctb.CaretIndex;            combobox.IsDropDownOpen = true;
            var tempValue = combobox.SelectedValue;
            var datasource = (combobox.ItemsSource as List<SelectOption>).DeepClone()                .Where(x => /*自定义条件*/)                .ToList();            combobox.ItemsSource = datasource;
            CollectionView itemsViewOriginal = (CollectionView)CollectionViewSource.GetDefaultView(combobox.Items);
            itemsViewOriginal.Refresh();            combobox.SelectedValue = tempValue;            ctb.CaretIndex = caretPos;        }    }    /// <summary>    /// 下拉框数据源还原    /// </summary>  private void OnDropDownClosed(object sender, EventArgs e)    {        var cb = (ComboBox)sender;        if (cb.IsDropDownOpen == false)        {            var tempValue = cb.SelectedValue;            cb.ItemsSource = (this.DataContext as /*定义的前端ViewModel*/).source;            cb.SelectedValue = tempValue;
        }    }