Microsoft Reporting: Setting subreport parameters in code

Question

How can I set a parameter of a sub-report? I have successfully hooked myself up to the SubreportProcessing event, I can find the correct sub-report through e.ReportPath, and I can add datasources through e.DataSources.Add. But I find no way of adding report parameters??

I have found people suggesting to add them to the master report, but I don't really want to do that, since the master report shouldn't have to be connected to the sub-report at all, other than that it is wrapping the sub-report.

I am using one report as a master template, printing name of the report, page numbers etc. And the subreport is going to be the report itself. And if I could only find a way to set those report parameters of the sub-report I would be good to go...

Clarification: Creating/Defining the parameters is not the problem. The problem is to set their values. I thought the natural thing to do was to do it in the SubreportProcessing event. And the SubreportProcessingEventArgs do in fact have a Parameters property. But it is read only! So how do you use that? How can I set their value?

Answer 1

It does work but it sure is persnickety.

First thing I recommend is to develop your reports as .rdl. Much easier to test the reports this way. You can also get the subreport parameters set up and tested as rdl, making sure each parameter of the subreport is also defined as a parameter of the parent report. Once you get the reports - including the subreports - working that way you can rename the .rdl to rdlc and add the rdlc files to your ReportViewer Project. No further changes required. Use the names of the rdl datasources as the data source names in your code to provide data to the report in the SubreportProcessing event handler.

You don't assign values to the passed parameter. The subreport will use them as is. (Sounds like the step you are missing is adding the parameters to the parent report as well as the the subreport as mentioned above.) You can evaluate the parameters and use them as query parameters to get the datasource you will add. You have to think about the datasource like its on an undiscovered dimension for a subreport. You will have to poke around while debugging in the event handler to see what I mean. Some of the values in your application will be readily available, others that you use easily elsewhere will throw object not found exceptions. For example I create a dataset in a instance of a class created on my applications main form. I use the data set throughout my application. In the SubreportProcessing event handler I cannot use the common dataset, so I must create a new instance of the table I need for the report and populate it. In the main report I would be able to access the common dataset. There are other limitations like this. Just have to wade your way through.

Here is the SubreportProcessing event handler from a working VB.NET ReportViewer application. Shows a few different ways to get the datasource for a subreport. subreport1 builds a one row datatable from application business objects, subreport2 provides data the report requires without a parameter, subreport3 is lie subreport2 but evaluates one of the parameters passed to the subreport for use in date value required by the query that creates the ReportDataSource.

    Public Sub SubreportProcessingEventHandler(ByVal sender As Object, _
                                               ByVal e As SubreportProcessingEventArgs)
    Select Case e.ReportPath
        Case "subreport1"
            Dim tbl As DataTable = New DataTable("TableName")
            Dim Status As DataColumn = New DataColumn
            Status.DataType = System.Type.GetType("System.String")
            Status.ColumnName = "Status"
            tbl.Columns.Add(Status)
            Dim Account As DataColumn = New DataColumn
            Account.DataType = System.Type.GetType("System.String")
            Account.ColumnName = "Account"
            tbl.Columns.Add(Account)
            Dim rw As DataRow = tbl.NewRow()
            rw("Status") = core.GetStatus
            rw("Account") = core.Account
            tbl.Rows.Add(rw)
            e.DataSources.Add(New ReportDataSource("ReportDatasourceName", tbl))
        Case "subreport2"
            core.DAL.cnStr = My.Settings.cnStr
            core.DAL.LoadSchedule()
            e.DataSources.Add(New ReportDataSource("ScheduledTasks", _
                                                   My.Forms.Mother.DAL.dsSQLCfg.tSchedule))
        Case "subreport3"
            core.DAL.cnStr = My.Settings.cnStr
            Dim dt As DataTable = core.DAL.GetNodesForDateRange(DateAdd("d", _
                                                                          -1 * CInt(e.Parameters("NumberOfDays").Values(0)), _
                                                                          Today), _
                                                                  Now)
            e.DataSources.Add(New ReportDataSource("Summary", dt))
    End Select
End Sub