WPF中如何阻止ComboBox滚动但允许父UIElement滚动？

我需要在ComboBox获得**focused（焦点）**时，阻止其通过滚轮滚动。
但同时要允许它的父UIElement正常滚动。
我从相关问题中获取了以下代码，但该代码会阻止所有滚动，包括父UIElement的滚动。

XAML代码 #

<ComboBox comboBox:NoScrollingBehaviour.Enabled="True"
          IsEditable="True" 
          IsTextSearchEnabled="True" 
          IsTextSearchCaseSensitive="False" 
          StaysOpenOnEdit="True"
          Text="{Binding MyTextProperty}"
          ItemsSource="{Binding DataContext.MySourceProperty, ElementName=MyElementName}"/>

C#行为代码 #

using System.Windows;
using System.Windows.Input;

namespace AE.UI.ComboBox
{
    public static class NoScrollingBehaviour
    {
        public static readonly DependencyProperty EnabledProperty =
            DependencyProperty.RegisterAttached("Enabled", typeof(bool), typeof(NoScrollingBehaviour),
                                                new UIPropertyMetadata(false, OnEnabledChanged));

        public static bool GetEnabled(System.Windows.Controls.ComboBox comboBox) => (bool)comboBox.GetValue(EnabledProperty);

        public static void SetEnabled(System.Windows.Controls.ComboBox comboBox, bool value) => comboBox.SetValue(EnabledProperty, value);

        private static void OnEnabledChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var comboBox = (System.Windows.Controls.ComboBox)d;
            if (GetEnabled(comboBox))
                comboBox.PreviewMouseWheel += OnPreviewMouseWheel;
        }

        private static void OnPreviewMouseWheel(object sender, MouseWheelEventArgs e)
        {
            var comboBox = (System.Windows.Controls.ComboBox)sender;
            if (!GetEnabled(comboBox))
                return;
            
            if (comboBox.IsDropDownOpen)
                return;

            e.Handled = true;
        }
    }
}

如何在阻止ComboBox滚动的同时，允许父UIElement继续滚动？

解决方案 #

原代码中e.Handled = true会直接终止事件路由，导致父元素无法接收滚轮事件。我们需要修改逻辑，让事件能传递给父级可滚动元素，同时阻止ComboBox自身响应。

修改后的NoScrollingBehaviour代码如下：

using System.Windows;
using System.Windows.Input;
using System.Windows.Media;

namespace AE.UI.ComboBox
{
    public static class NoScrollingBehaviour
    {
        public static readonly DependencyProperty EnabledProperty =
            DependencyProperty.RegisterAttached("Enabled", typeof(bool), typeof(NoScrollingBehaviour),
                                                new UIPropertyMetadata(false, OnEnabledChanged));

        public static bool GetEnabled(System.Windows.Controls.ComboBox comboBox) => (bool)comboBox.GetValue(EnabledProperty);

        public static void SetEnabled(System.Windows.Controls.ComboBox comboBox, bool value) => comboBox.SetValue(EnabledProperty, value);

        private static void OnEnabledChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var comboBox = (System.Windows.Controls.ComboBox)d;
            if ((bool)e.NewValue)
                comboBox.PreviewMouseWheel += OnPreviewMouseWheel;
            else
                comboBox.PreviewMouseWheel -= OnPreviewMouseWheel;
        }

        private static void OnPreviewMouseWheel(object sender, MouseWheelEventArgs e)
        {
            var comboBox = (System.Windows.Controls.ComboBox)sender;
            if (!GetEnabled(comboBox) || comboBox.IsDropDownOpen)
                return;

            // 向上查找第一个可滚动的父元素
            var parent = VisualTreeHelper.GetParent(comboBox);
            while (parent != null && !(parent is IScrollInfo))
            {
                parent = VisualTreeHelper.GetParent(parent);
            }

            if (parent is UIElement scrollableParent)
            {
                // 创建新的滚轮事件并传递给父元素
                var newEvent = new MouseWheelEventArgs(e.MouseDevice, e.Timestamp, e.Delta)
                {
                    RoutedEvent = UIElement.MouseWheelEvent
                };
                scrollableParent.RaiseEvent(newEvent);
            }
        }
    }
}

关键修改说明 #

1. 添加事件清理逻辑：在OnEnabledChanged中根据属性值的变化，动态添加或移除事件处理，避免内存泄漏。
2. 事件传递而非终止：不再设置e.Handled = true，而是通过视觉树找到父级可滚动元素（如ScrollViewer），手动触发其滚轮事件，保证父元素正常滚动。
3. 保留原有判断：依然保留IsDropDownOpen的判断，当下拉框展开时，允许ComboBox正常滚动选项。

内容的提问来源于stack exchange，提问作者Tyler