Creating subreport in cystal report

Question

I have created this model object in C# and want to create a report with sub report and don't know how to link the 2; Here is my model

public class LabReport
{
public int ref_id{get;set;}
public String t_name { get; set; }
public IList<LabSubReport> result { get; set; }//this where i need subreport
}
public class LabSubReport
{
public int ref_id { get; set; }//foreign key from Above model
public String l_test { get; set; }
public String t_value { get; set; }
}

and this is how Have populated my model

IList<LabReport> report=report=new List<LabReport>();
IList<LabRequestEntity> empo =//dao to fetch data
int count = 1;
foreach (LabRequestEntity e in empo)
{
    IList<LabTestNoteEntity>  notes=e.test_note;//entity relation ship here
    IList<LabSubReport> sublist=new List<LabSubReport>();


    foreach(LabTestNoteEntity p in notes)
    {
       var sub=new LabSubReport()
       {
          l_test=p.test,
          t_value=p.result
       };
        sublist.Add(sub);
    }

    var rpt = new LabReport()
    {
        ref_id = "" + count,
        t_name=e.lab_test.t_name,
        result=sublist

    };
    count++;
    report.Add(rpt);

}

And I would wish my report to look this way. Where its highlighted with blue is where i need the sub-report to be

 

 

 

I have tried this

ReportDocument cryRpt = new ReportDocument();
cryRpt.Load("C:/MainReport.rpt");
cryRpt.DataSourceConnections.Clear();
cryRpt.SetDataSource(report);
cryRpt.Subreports[0].DataSourceConnections.Clear();
cryRpt.Subreports[0].SetDataSource(report.select(x=>x.result));

and getting this error

 

Column 'ref_id' does not belong to table LabSubReport