多态组合控件：文本框；文本框+下拉表格；只读文本框+下拉表格,下拉表格可排序。可用作其它表格控件的编辑控件。-Polymorphic composition controls: text box text box+ Drop-down form read-only text box+ Drop-down form, the drop-down forms can be sorted. Other controls can be used as a form edit control.