how can back up of database

create folder with name of  backup

SqlConnection con = new SqlConnection("Data Source=aa\\

SQLEXPRESS;Initial Catalog=aa;Integrated Security=True");
        SqlCommand cmd = new SqlCommand("backup database aa to disk = '" + Server.MapPath("~/backup/aa.bak") + "' ", con);
        con.Open();
        cmd.ExecuteNonQuery();
        con.Close();