Load Report Failed error shows what is the problem from my code.from the code please correct it.

            con.Open();
            string str = "select * from diesel where Billno='" + cb_billno.SelectedItem + "'";
            SqlCommand com = new SqlCommand(str, con);
            SqlDataAdapter sqlda = new SqlDataAdapter(com);
            DataSet ds = new DataSet();
            sqlda.Fill(ds, "diesel");
            con.Close();
 
            ReportDocument r1 = new ReportDocument();
            r1.Load("Reports/Service Bill.rpt");
            r1.SetDataSource(ds);
            crystalReportViewer1.ReportSource = r1;
            crystalReportViewer1.RefreshReport();