@Bryce，回答得很好。

VB。净版:

Public Shared Iterator Function FindVisualChildren(Of T As DependencyObject)(depObj As DependencyObject) As IEnumerable(Of T)
    If depObj IsNot Nothing Then
        For i As Integer = 0 To VisualTreeHelper.GetChildrenCount(depObj) - 1
            Dim child As DependencyObject = VisualTreeHelper.GetChild(depObj, i)
            If child IsNot Nothing AndAlso TypeOf child Is T Then
                Yield DirectCast(child, T)
            End If
            For Each childOfChild As T In FindVisualChildren(Of T)(child)
                Yield childOfChild
            Next
        Next
    End If
End Function

用法(这将禁用窗口中的所有文本框):

        For Each tb As TextBox In FindVisualChildren(Of TextBox)(Me)
          tb.IsEnabled = False
        Next

下面是另一个紧凑的版本，使用泛型语法:

    public static IEnumerable<T> FindLogicalChildren<T>(DependencyObject obj) where T : DependencyObject
    {
        if (obj != null) {
            if (obj is T)
                yield return obj as T;

            foreach (DependencyObject child in LogicalTreeHelper.GetChildren(obj).OfType<DependencyObject>()) 
                foreach (T c in FindLogicalChildren<T>(child)) 
                    yield return c;
        }
    }

对递归做了一点小小的改变，例如，你可以找到一个标签控件的子标签控件。

    public static DependencyObject FindInVisualTreeDown(DependencyObject obj, Type type)
    {
        if (obj != null)
        {
            for (int i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)
            {
                DependencyObject child = VisualTreeHelper.GetChild(obj, i);

                if (child.GetType() == type)
                {
                    return child;
                }

                DependencyObject childReturn = FindInVisualTreeDown(child, type);
                if (childReturn != null)
                {
                    return childReturn;
                }
            }
        }

        return null;
    }

接受的答案返回发现的元素或多或少是无序的，方法是尽可能深入地跟随第一个子分支，同时在返回和重复尚未解析的树枝的步骤之前，沿途生成发现的元素。

如果你需要按降序排列的后代元素，其中直接的子元素将首先产生，然后是它们的子元素，依此类推，下面的算法将工作:

public static IEnumerable<T> GetVisualDescendants<T>(DependencyObject parent, bool applyTemplates = false)
    where T : DependencyObject
{
    if (parent == null || !(child is Visual || child is Visual3D))
        yield break;

    var descendants = new Queue<DependencyObject>();
    descendants.Enqueue(parent);

    while (descendants.Count > 0)
    {
        var currentDescendant = descendants.Dequeue();

        if (applyTemplates)
            (currentDescendant as FrameworkElement)?.ApplyTemplate();

        for (var i = 0; i < VisualTreeHelper.GetChildrenCount(currentDescendant); i++)
        {
            var child = VisualTreeHelper.GetChild(currentDescendant, i);

            if (child is Visual || child is Visual3D)
                descendants.Enqueue(child);

            if (child is T foundObject)
                yield return foundObject;
        }
    }
}

生成的元素将从最近到最远进行排序。 这将是有用的，例如，如果你正在寻找某种类型和条件的最近的子元素:

var foundElement = GetDescendants<StackPanel>(someElement)
                       .FirstOrDefault(o => o.SomeProperty == SomeState);

请注意，使用VisualTreeHelper仅适用于派生自Visual或Visual3D的控件。如果你还需要检查其他元素(例如TextBlock, FlowDocument等)，使用VisualTreeHelper将抛出一个异常。

如果有必要，这里有一个回到逻辑树的替代方案:

http://www.hardcodet.net/2009/06/finding-elements-in-wpf-tree-both-ways

这就是它向上的工作原理

    private T FindParent<T>(DependencyObject item, Type StopAt) where T : class
    {
        if (item is T)
        {
            return item as T;
        }
        else
        {
            DependencyObject _parent = VisualTreeHelper.GetParent(item);
            if (_parent == null)
            {
                return default(T);
            }
            else
            {
                Type _type = _parent.GetType();
                if (StopAt != null)
                {
                    if ((_type.IsSubclassOf(StopAt) == true) || (_type == StopAt))
                    {
                        return null;
                    }
                }

                if ((_type.IsSubclassOf(typeof(T)) == true) || (_type == typeof(T)))
                {
                    return _parent as T;
                }
                else
                {
                    return FindParent<T>(_parent, StopAt);
                }
            }
        }
    }