基于WPF实现多选下拉控件的示例代码

WPF 实现多选下拉控件

框架使用.NET40；

Visual Studio 2022;

创建控件 MultiSelectComboBox 继承 ListBox 。

• 依赖属性 IsSelectAllActive 是否支持显示全选，默认 false 。
• 依赖属性 SelectAllContent 全选控件的 Content，默认显示 全选 。
• 依赖属性 Delimiter 分隔符，默认显示 ; 。
• 依赖属性 Text 显示选择的所有 Item 。
• 其他与ComboBox 依赖属性一致。

实现代码

1） MultiSelectComboBox.xaml 代码如下：

using System;
using System.ComponentModel;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Input;
using System.Windows.Threading;

namespace WPFDevelopers.Controls
{
    public class MultiSelectComboBox : ListBox
    {
        private const string PART_Popup = "PART_Popup";
        private const string PART_CheckBoxAll = "PART_CheckBoxAll";

        public static readonly DependencyProperty IsDropDownOpenProperty =
            DependencyProperty.Register("IsDropDownOpen", typeof(bool), typeof(MultiSelectComboBox),
                new PropertyMetadata(false));

        public static readonly DependencyProperty MaxDropDownHeightProperty
            = DependencyProperty.Register("MaxDropDownHeight", typeof(double), typeof(MultiSelectComboBox),
                new PropertyMetadata(SystemParameters.PrimaryScreenHeight / 3));

        public static readonly DependencyProperty SelectAllContentProperty =
            DependencyProperty.Register("SelectAllContent", typeof(object), typeof(MultiSelectComboBox),
                new PropertyMetadata("全选"));

        public static readonly DependencyProperty IsSelectAllActiveProperty =
            DependencyProperty.Register("IsSelectAllActive", typeof(bool), typeof(MultiSelectComboBox),
                new PropertyMetadata(false));

        public static readonly DependencyProperty DelimiterProperty =
            DependencyProperty.Register("Delimiter", typeof(string), typeof(MultiSelectComboBox),
                new PropertyMetadata(";"));

        public static readonly DependencyProperty TextProperty =
            DependencyProperty.Register("Text", typeof(string), typeof(MultiSelectComboBox),
                new PropertyMetadata(string.Empty, OnTextChanged));

        private bool _ignoreTextValueChanged;
        private MultiSelectComboBoxItem _multiSelectComboBoxItem;
        private Popup _popup;

        public bool IsDropDownOpen
        {
            get => (bool)GetValue(IsDropDownOpenProperty);
            set => SetValue(IsDropDownOpenProperty, value);
        }


        [Bindable(true)]
        [Category("Layout")]
        [TypeConverter(typeof(LengthConverter))]
        public double MaxDropDownHeight
        {
            get => (double)GetValue(MaxDropDownHeightProperty);
            set => SetValue(MaxDropDownHeightProperty, value);
        }


        public object SelectAllContent
        {
            get => GetValue(SelectAllContentProperty);
            set => SetValue(SelectAllContentProperty, value);
        }


        public bool IsSelectAllActive
        {
            get => (bool)GetValue(IsSelectAllActiveProperty);
            set => SetValue(IsSelectAllActiveProperty, value);
        }


        public string Delimiter
        {
            get => (string)GetValue(DelimiterProperty);
            set => SetValue(DelimiterProperty, value);
        }


        public string Text
        {
            get => (string)GetValue(TextProperty);
            set => SetValue(TextProperty, value);
        }

        private static void OnIsDropDownOpenChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var MultiSelectComboBox = (MultiSelectComboBox)d;

            if (!(bool)e.NewValue)
                MultiSelectComboBox.Dispatcher.BeginInvoke(new Action(() => { Mouse.Capture(null); }),
                    DispatcherPriority.Send);
        }

        private static void OnTextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
        }


        protected override bool IsItemItsOwnContainerOverride(object item)
        {
            return item is MultiSelectComboBoxItem;
        }

        protected override DependencyObject GetContainerForItemOverride()
        {
            return new MultiSelectComboBoxItem();
        }

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

        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();

            _popup = GetTemplateChild(PART_Popup) as Popup;
            _multiSelectComboBoxItem = GetTemplateChild(PART_CheckBoxAll) as MultiSelectComboBoxItem;
            _multiSelectComboBoxItem.Selected += _MultiSelectComboBoxItem_Selected;
            _multiSelectComboBoxItem.Unselected += _MultiSelectComboBoxItem_Unselected;
        }

        private void _MultiSelectComboBoxItem_Unselected(object sender, RoutedEventArgs e)
        {
            if (_ignoreTextValueChanged) return;
            _ignoreTextValueChanged = true;
            UnselectAll();
            _ignoreTextValueChanged = false;
            UpdateText();
        }

        private void _MultiSelectComboBoxItem_Selected(object sender, RoutedEventArgs e)
        {
            if (_ignoreTextValueChanged) return;
            _ignoreTextValueChanged = true;
            SelectAll();
            _ignoreTextValueChanged = false;
            UpdateText();
        }

        protected virtual void UpdateText()
        {
            if (_ignoreTextValueChanged) return;
            var newValue = string.Join(Delimiter, SelectedItems.Cast