<UserControl x:Class="ToolsTest.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
    mc:Ignorable="d" d:DesignWidth="640" d:DesignHeight="480">
  <Grid x:Name="LayoutRoot">      
        <StackPanel x:Name="sp" HorizontalAlignment="Left">
            <TextBlock Text="Test TextBlock" Height="25" Width="100" x:Name="txt"></TextBlock>
            <Button x:Name="btn1" Content="button1" Height="25" Width="100" ></Button>
            <StackPanel x:Name="sp2">
                <Button x:Name="btn2" Content="button2" Height="25" Width="100" ></Button>
            </StackPanel>
            <Button x:Name="btn3" Content="button3"></Button>
        </StackPanel>
        <Button x:Name="btnClick" Content="Test" Height="22" Width="80" HorizontalAlignment="Center" VerticalAlignment="Bottom" Click="btnClick_Click" ></Button>
  </Grid>
</UserControl>

using System.Linq;
using System.Windows;
using System.Collections.Generic;
using System.Windows.Controls;
using System.Windows.Media;

namespace ToolsTest
{
    public partial class MainPage : UserControl
    {
        public MainPage()
        {
            InitializeComponent();
        }

private void btnClick_Click(object sender, RoutedEventArgs e)
        {
            int _childCount = VisualTreeHelper.GetChildrenCount(this);
            MessageBox.Show("MainPage下级子对象总数：" + _childCount.ToString());//就是一个Grid，所以返回1

IEnumerable<Button> AllButtons = FindChildren<Button>(this);//得到所有的Buttons

int i =0;
            foreach (Button btn in AllButtons)
            {
                i++;
                MessageBox.Show(string.Format("第{0}个按钮[{1}]的内容为：{2}",i,btn.Name,btn.Content));                
            }

StackPanel sp = VisualTreeHelper.GetParent(btn2) as StackPanel;
            MessageBox.Show(string.Format("{0}的上级对象是{1}",btn2.Content,sp.Name));

Rect rect = new Rect(0, 0, 100, 25);

IEnumerable<UIElement> check = VisualTreeHelper.FindElementsInHostCoordinates(rect, this); //检测MainPage的0,0到100,25矩形区域内有哪些元素

foreach (UIElement item in check)
            {
                string _name = item.GetValue(NameProperty).ToString();
                if (_name.Length > 0)
                {
                    MessageBox.Show(_name);
                }
            }           
        }

/// <summary>
        /// 来自博客园"木野狐"的特定类型子对象方法
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="parent"></param>
        /// <returns></returns>
        public IEnumerable<T> FindChildren<T>(DependencyObject parent) where T : class
        {
            var count = VisualTreeHelper.GetChildrenCount(parent);
            if (count > 0)
            {
                for (var i = 0; i < count; i++)
                {
                    var child = VisualTreeHelper.GetChild(parent, i);
                    var t = child as T;
                    if (t != null)
                        yield return t;

var children = FindChildren<T>(child);
                    foreach (var item in children)
                        yield return item;
                }
            }
        }
    }
}