水晶报表子报表显示不了?

[fipamw]

//主报表
sql = "select a.pat_code,a.reg_times,a.pat_name from tj_patient a,tj_register b where a.pat_code = b.pat_code and a.reg_times = b.reg_times " + sqlWhereString;
SqlDataAdapter sqlAd = new SqlDataAdapter(sql,MyConn);
DataSet ds = new DataSet();
sqlAd.Fill(ds);
Rpt_Tj_Report myRpt = new Rpt_Tj_Report();
//子报表
sql = "select a.comb_code,a.doct_name,a.res_tag,b.item_code,b.rec_result,b.unit from tj_record a,tj_record_entry b where a.rec_no = b.rec_no and a.reg_no = '"+ ls_reg_no +"'";
SqlDataAdapter sqlAd_detail = new SqlDataAdapter(sql,MyConn);
DataSet ds_detail = new DataSet();
sqlAd_detail.Fill(ds_detail);
SubreportObject oSubreport1 = myRpt.ReportFooterSection1.ReportObjects["Subreport1"] as SubreportObject;
ReportDocument oSub1 = oSubreport1.OpenSubreport("Rpt_Tj_Report_Detail");
oSub1.SetDataSource(ds_detail);
//绑定
myRpt.SetDataSource(ds);

不知道为什么,我的子报表就是显示不出来
crv_Report.ReportSource = myRpt;
MyConn.Close();