Ajuda com Mysql em VS??

public class ConexaoSQL
    {
        private String strCon = "Server=localhost; Port=3306; DataBase=raphaelsantos; Uid=raphaelsantos; Pwd=123;";
        private MySqlConnection conn;

        public bool verificarUsuario(String cpf, String senha)
        {
            bool status = false;
            int retorno;
            conn = new MySqlConnection(strCon);
            String SQL = "select count(*) from usuarios where (cpf="+cpf+"and senha="+senha+")";
            MySqlCommand cmd = new MySqlCommand(SQL, conn);
            conn.Open();
            retorno = (int)cmd.ExecuteScalar();

            if (retorno > 0)
                status = true;
            return status;
        }
    }