SubreportProcessingEventHandler is not firing even without parameters in the subreport - rdlc

Question

I'm trying to use the subreport component in my main report but does not fire the event SubreportProcessingEventHandler even without any parameter in the sub-report that can generate any errors.
public ActionResult MyReport(DateTime dateReport)
{
var root = Path.GetDirectoryName(this.Server.MapPath("~"));
if (string.IsNullOrEmpty(root))
{
return this.HttpNotFound();
}
var path = Path.Combine(root, "bin\\Reports\\MainReport.rdlc");
if (System.IO.File.Exists(path))
{
this.reportViewer.LocalReport.ReportPath = path;
}
else
{
return this.View("Index");
}
this.LoadData(dateReport);
var reportType = "PDF";
string mimeType;
string encoding;
string fileNameExtension;
var deviceInfo = "<DeviceInfo>" + " <OutputFormat>" + reportType + "</OutputFormat>"
+ " <PageWidth>8.5in</PageWidth>" + " <PageHeight>11in</PageHeight>"
+ " <MarginTop>0.2in</MarginTop>" + " <MarginLeft>0.4in</MarginLeft>"
+ " <MarginRight>0.4in</MarginRight>" + " <MarginBottom>0.1in</MarginBottom>"
+ "</DeviceInfo>";
Warning[] warnings;
string[] streams;
var renderedBytes = this.reportViewer.LocalReport.Render(
reportType,
deviceInfo,
out mimeType,
out encoding,
out fileNameExtension,
out streams,
out warnings);
return this.File(renderedBytes, mimeType);
}
private void LoadData(DateTime dateReport)
{
........
this.reportViewer.LocalReport.SubreportProcessing += new SubreportProcessingEventHandler(this.MySubreportEventHandler);
this.reportViewer.LocalReport.DataSources.Add(new ReportDataSource("UserDataSet", users.DistinctBy(u => u.UserName)));
this.reportViewer.LocalReport.DataSources.Add(new ReportDataSource("EluateReportDataSet", radiopharmacyEluateReports));
this.reportViewer.LocalReport.DataSources.Add(new ReportDataSource("MarkingProtocolReportDataSet", radiopharmacyMarkingProtocolReports));
this.reportViewer.LocalReport.Refresh();
}
public void MySubreportEventHandler(object sender, SubreportProcessingEventArgs e)
{
.....
e.DataSources.Add(new ReportDataSource("RadiopharmaceuticalQualityControlDataSet", radiopharmacyReportQualityControls));
}
I have checked the output and this warning is raised:
Warning: Warnings occurred while executing the subreport ‘Subreport1’. (rsWarningExecutingSubreport)

Answer 1

After more detailed observation, i noticed that subreport really need an parameter that matches with a parameter passed by main report. Without any parameter the subreport just don't work.