ComboBox中的UWP TemplatePart

Question

为什么ComboBox中没有TemplatePartAttribute？

UWP：

public ActionResult subcategory(string brand, ..., Dictionary<string, string> filters)
{
    foreach(KeyValuePair<string, int> item in filters)
    {
        int category = Convert.ToInt32(item.Key.Split('-')[0]);
        int filter = item.Value;
    }
}

WPF：

[Composable(typeof(IComboBoxFactory), CompositionType.Public, 65536, "Windows.Foundation.UniversalApiContract")]
[ContractVersion(typeof(UniversalApiContract), 65536)]
[MarshalingBehavior(MarshalingType.Agile)]
[Static(typeof(IComboBoxStatics2), 65536, "Windows.Foundation.UniversalApiContract")]
[Static(typeof(IComboBoxStatics), 65536, "Windows.Foundation.UniversalApiContract")]
[Threading(ThreadingModel.Both)]
[WebHostHidden]
public class ComboBox : Selector, IComboBox, IComboBoxOverrides, IComboBox2