R – way to add a subreport to the header of an RDLC report

You could set an IIF statement on the Visibility property of the control you want to hide.

=IIF(ROWCOUNT=0, FALSE, TRUE)

That way, the report will not render that control if there is no data. you can even take it a step further, and make another control appear when no data is present, to display a message ("There is no data")

• Goto SubReport -> Report Data Pane -> Parameters and add the parameter you want to receive.

• Goto MainReport -> Right-click SubReport -> Subreport Properties -> Parameters and add the same paramter name and pick the relevant value from the dropdown.

• Handle the SubreportProcessing event and set the datasource for the subreport. In my case the main report datasource was of type List<Order> and the parameter was OrderID. Sample code below.

ReportViewer1.LocalReport.SubreportProcessing += new SubreportProcessingEventHandler(SetSubDataSource);

public void SetSubDataSource(object sender, SubreportProcessingEventArgs e)
{
    var mainSource = ((LocalReport) sender).DataSources["MainDataSet1"];
    var orderId = int.Parse(e.Parameters["OrderID"].Values.First());
    var subSource = ((List<Order>)mainSource.Value).Single(o => o.OrderID == orderId).Suppliers;
    e.DataSources.Add(new ReportDataSource("SubDataSet1", subSource));
}