我发现没有Visual Tree Helpers更容易:

foreach (UIElement element in MainWindow.Children) {
    if (element is TextBox) { 
        if ((element as TextBox).Text != "")
        {
            //Do something
        }
    }
};

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

使用帮助类VisualTreeHelper或LogicalTreeHelper，这取决于你对哪棵树感兴趣。它们都提供了获取元素的子元素的方法(尽管语法略有不同)。我经常使用这些类来查找特定类型的第一个出现，但你可以很容易地修改它来查找该类型的所有对象:

public static DependencyObject FindInVisualTreeDown(DependencyObject obj, Type type)
{
    if (obj != null)
    {
        if (obj.GetType() == type)
        {
            return obj;
        }

        for (int i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)
        {
            DependencyObject childReturn = FindInVisualTreeDown(VisualTreeHelper.GetChild(obj, i), type);
            if (childReturn != null)
            {
                return childReturn;
            }
        }
    }

    return null;
}

@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

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;
    }

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);
                }
            }
        }
    }