wpf treeview 扩展图标和checkbox多选功能

WPF TreeView 控件默认提供了展开/折叠图标和单个CheckBox选中功能，如果需要实现扩展图标和多选功能，可以通过自定义TreeViewItem样式来实现。

下面是一个简单的示例，展示如何在WPF TreeView中实现扩展图标和多选功能：

1. 创建一个自定义TreeViewItem样式，并在其中添加一个扩展图标和多选CheckBox：

<Style x:Key="TreeViewItemStyle" TargetType="{x:Type TreeViewItem}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type TreeViewItem}">
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto"/>
                        <ColumnDefinition/>
                    </Grid.ColumnDefinitions>
                    <StackPanel Orientation="Horizontal" Grid.Column="0">
                        <Image x:Name="ExpandCollapseImage" Source="Expand.png" Width="16" Height="16" Margin="0,0,5,0"
                               Visibility="Collapsed" />
                        <CheckBox x:Name="CheckBox" VerticalAlignment="Center" Margin="0,0,5,0"/>
                        <ContentPresenter ContentSource="Header" />
                    </StackPanel>
                    <ItemsPresenter Grid.Column="1" />
                </Grid>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsExpanded" Value="True">
                        <Setter TargetName="ExpandCollapseImage" Property="Source" Value="Collapse.png" />
                        <Setter TargetName="ExpandCollapseImage" Property="Visibility" Value="Visible" />
                    </Trigger>
                    <MultiTrigger>
                        <MultiTrigger.Conditions>
                            <Condition Property="IsSelected" Value="True"/>
                            <Condition Property="IsSelectionActive" Value="True"/>
                        </MultiTrigger.Conditions>
                        <Setter TargetName="CheckBox" Property="IsChecked" Value="True"/>
                    </MultiTrigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

2. 在TreeView中应用自定义样式：

<TreeView x:Name="TreeView" ItemContainerStyle="{StaticResource TreeViewItemStyle}">
    <!-- 树节点内容 -->
</TreeView>

3. 处理TreeViewItem的展开/折叠事件：

private void TreeViewItem_Expanded(object sender, RoutedEventArgs e)
{
    TreeViewItem item = e.OriginalSource as TreeViewItem;
    if (item != null)
    {
        Image image = FindChild<Image>(item, "ExpandCollapseImage");
        if (image != null)
        {
            image.Source = new BitmapImage(new Uri("Collapse.png", UriKind.Relative));
        }
    }
}

private void TreeViewItem_Collapsed(object sender, RoutedEventArgs e)
{
    TreeViewItem item = e.OriginalSource as TreeViewItem;
    if (item != null)
    {
        Image image = FindChild<Image>(item, "ExpandCollapseImage");
        if (image != null)
        {
            image.Source = new BitmapImage(new Uri("Expand.png", UriKind.Relative));
        }
    }
}

private T FindChild<T>(DependencyObject parent, string childName) where T : DependencyObject
{
    if (parent == null) return null;

    T child = null;
    int childrenCount = VisualTreeHelper.GetChildrenCount(parent);
    for (int i = 0; i < childrenCount; i++)
    {
        DependencyObject childElement = VisualTreeHelper.GetChild(parent, i);
        if (childElement is T && ((FrameworkElement)childElement).Name == childName)
        {
            child = (T)childElement;
            break;
        }
        else
        {
            child = FindChild<T>(childElement, childName);
            if (child != null) break;
        }
    }

    return child;
}

4. 处理TreeViewItem的多选事件：

private void CheckBox_Click(object sender, RoutedEventArgs e)
{
    TreeViewItem item = FindParent<TreeViewItem>(sender as DependencyObject);
    if (item != null)
    {
        // 获取父节点
        TreeViewItem parentItem = FindParent<TreeViewItem>(item.Parent);
        if (parentItem != null)
        {
            // 获取所有子节点
            List<TreeViewItem> childItems = new List<TreeViewItem>();
            GetChildItems(parentItem, childItems);

            // 更新所有节点的多选状态
            foreach (TreeViewItem childItem in childItems)
            {
                CheckBox checkBox = FindChild<CheckBox>(childItem, "CheckBox");
                if (checkBox != null)
                {
                    checkBox.IsChecked = GetChildCheckedState(parentItem);
                }
            }
        }
    }
}

private TreeViewItem FindParent<T>(DependencyObject child) where T : DependencyObject
{
    if (child == null) return null;

    DependencyObject parent = VisualTreeHelper.GetParent(child);

    while (parent != null && !(parent is T))
    {
        parent = VisualTreeHelper.GetParent(parent);
    }

    return parent as TreeViewItem;
}

private void GetChildItems(TreeViewItem item, List<TreeViewItem> childItems)
{
    int childrenCount = VisualTreeHelper.GetChildrenCount(item);

    for (int i = 0; i < childrenCount; i++)
    {
        DependencyObject childElement = VisualTreeHelper.GetChild(item, i);
        if (childElement is TreeViewItem)
        {
            childItems.Add(childElement as TreeViewItem);
            GetChildItems(childElement as TreeViewItem, childItems);
        }
    }
}

private bool GetChildCheckedState(TreeViewItem parent)
{
    int childrenCount = VisualTreeHelper.GetChildrenCount(parent);
    bool isChecked = false;

    for (int i = 0; i < childrenCount; i++)
    {
        DependencyObject childElement = VisualTreeHelper.GetChild(parent, i);
        if (childElement is TreeViewItem)
        {
            CheckBox checkBox = FindChild<CheckBox>(childElement as TreeViewItem, "CheckBox");
            if (checkBox != null && checkBox.IsChecked == true)
            {
                isChecked = true;
                break;
            }
            else
            {
                isChecked = GetChildCheckedState(childElement as TreeViewItem);
                if (isChecked) break;
            }
        }
    }

    return isChecked;
}

通过以上步骤，我们就可以在WPF TreeView中实现扩展图标和多选功能了。