WPF如何自定义隐藏下拉框选项

目前很多的Client都是基于JS的，但是总有时候会遇到其他的框架不如Qt、WPF和JavaFx等。那么这次我就讲解一个WPF的技巧：如何自定义隐藏下拉框选项

demo.xaml

                      KeyUp="comboBox_KeyUp" DropDownOpened="OnDropDownOpened" 	DropDownClosed="OnDropDownClosed"
/>

demo.xaml.cs

/// 

/// 搜索条件过滤
/// 
 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).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;
    }
	
	/// 

    /// 下拉框初始化过滤
    /// 
	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).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;
        }
    }
    /// 

    /// 下拉框数据源还原
    /// 
	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;

        }
    }

结语

原理看代码就会了，具体如何自定义过滤，结合自己的实际需求设计。