private void listarToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Listar list = new Listar();

            list.IsMdiContainer = false;
            list.Show();
        }
        private void button2_Click(object sender, EventArgs e)
        {
            Listar list = new Listar();

            list.IsMdiContainer = false;
            list.Show();
        }