在显示ContextMenu之前,右键单击选择TreeView节点

<TreeView MouseRightButtonDown="TreeView_MouseRightButtonDown">
    <!-- TreeView的内容 -->
</TreeView>

private void TreeView_MouseRightButtonDown(object sender, MouseButtonEventArgs e)
{
    // 获取右键单击的TreeViewItem
    TreeViewItem clickedItem = FindAncestor<TreeViewItem>((DependencyObject)e.OriginalSource);

    if (clickedItem != null)
    {
        // 在此处执行你想要的操作，例如选择节点、显示上下文菜单等
        clickedItem.IsSelected = true;
        e.Handled = true; // 防止TreeView默认的右键菜单显示
    }
}

// 辅助方法：查找指定类型的父级元素
private T FindAncestor<T>(DependencyObject current) where T : DependencyObject
{
    do
    {
        if (current is T ancestor)
        {
            return ancestor;
        }
        current = VisualTreeHelper.GetParent(current);
    }
    while (current != null);
    return null;
}