private void Button11_Click(object sender, EventArgs e)
        {
            Yao_s_Food_App form = new Yao_s_Food_App();

            form.ShowDialog();
            this.Hide();
        }
        private void Button11_Click(object sender, EventArgs e)
        {
            var form1 = new Yao_s_Food_App();

            form1.Closed += (s, args) => this.Close();
            form1.Show();
            this.Hide();
        }