如何为guna或bunifu框架foreach循环控件？我想检查一个文本框是否为空。

private void btn_save_Click(object sender, EventArgs e)
{
            foreach (Control obj in Panel.Controls)
            {
                //if using normal TextBox it work..
                if (obj is Guna2TextBox)
                {
                    if (obj.Text == "")
                    {
                        MessageBox.Show("Action connot be perform. All fields are required to be fill up.");
                        return;
                    }
                }
            }
}