public static bool HasValidationErrors(this DependencyObject parent)
{
    var stack = new Stack<DependencyObject>();
    foreach (var child in LogicalTreeHelper.GetChildren(parent).OfType<DependencyObject>())
        stack.Push(child);

    while (stack.Any())
    {
        var child = stack.Pop();
        if (Validation.GetErrors(child).Any())
            return true;

        foreach (var e in LogicalTreeHelper.GetChildren(child).OfType<DependencyObject>())
            stack.Push(e);
    }

    return false;
}