C#在WinForm中實現清空指定類型控制項的內容

實現在Winform中遞迴控制項來清空指定類型控制項的內容（因為在Winform中，各個控制項是有層次關係的，不能簡單地依靠遍曆this.controls）

private void ClearContent4Controls(Control.ControlCollection controls)
{
            foreach (Control c in controls)
            {
                if (c is TextBox)
                {
                    (c as TextBox).Text = string.Empty;
                }
                else if (c is ComboBox)
                {
                    (c as ComboBox).SelectedIndex = -1;
                }
                else if (c is CheckBox)
                {
                    (c as CheckBox).Checked = false;
                }

                ClearContent4Controls(c.Controls);
            }
}