private void ClearControl(Control sender)
        {
            foreach (Control item in sender.Controls)
            {
                if (item is CoreTextBox || item is CoreComboBox)
                {
                    item.text = string.Empty;
                    continue;
                }
                if (item.Controls.Count > 0)
                    ClearControl(item);
            }
        } 


小结：方法内可自调方法,即反复递归调用自身