public void CargarListado()
        {
            DataTable dt   = new DataTable();
            String    user = Program.ruc_empresa;

            dt = USER.ListarUsuario(user);
            try
            {
                dataGridView1.Rows.Clear();
                for (int i = 0; i < dt.Rows.Count; i++)
                {
                    dataGridView1.Rows.Add(dt.Rows[i][0]);
                    dataGridView1.Rows[i].Cells[0].Value = dt.Rows[i][0].ToString();
                    dataGridView1.Rows[i].Cells[1].Value = dt.Rows[i][1].ToString();
                    dataGridView1.Rows[i].Cells[2].Value = dt.Rows[i][2].ToString();
                    dataGridView1.Rows[i].Cells[3].Value = dt.Rows[i][3].ToString();
                    dataGridView1.Rows[i].Cells[4].Value = dt.Rows[i][4].ToString();
                    dataGridView1.Rows[i].Cells[5].Value = dt.Rows[i][5].ToString();
                    dataGridView1.Rows[i].Cells[6].Value = dt.Rows[i][6].ToString();
                    dataGridView1.Rows[i].Cells[7].Value = dt.Rows[i][7].ToString();
                    dataGridView1.Rows[i].Cells[8].Value = dt.Rows[i][8].ToString();
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            dataGridView1.ClearSelection();
        }