How do I write a function with variable classes in C#-CodePudding

I have the following bit of code in multiple places in my app:

var subReport = new XRptEventHeader();
var eventHeaderList = FreqReports.GetEventHeaderList(studyPK);
var dataSourceSubReport = (XRSubreport)oRpt.FindControl("xrSubreportSite", false);
dataSourceSubReport.ReportSource = subReport;
dataSourceSubReport.ReportSource.DataSource = eventHeaderList;

It is used in multiple places where the type for oRpt differs. I tried to use a generic something like this

public static T SetEventHeader<T>(T oRpt , Guid studyPK)
{
    var subReport = new XRptEventHeader();
    var eventHeaderList = FreqReports.GetEventHeaderList(studyPK);
    var dataSourceSubReport = (XtraReport)oRpt.FindControl("xrSubreportSite", false);
    dataSourceSubReport.ReportSource = subReport;
    dataSourceSubReport.ReportSource.DataSource = eventHeaderList;
    return oRpt;
}

But when I get to the line

var dataSourceSubReport = (XtraReport)oRpt.FindControl("xrSubreportSite", false);

and oRpt it doesn't have the FindControl function even when I cast with the base class of each class.

Does anyone have any suggestions on how I could get this to work?

CodePudding user response：

What you need to do is restrict the value of T to a base class or interface that all your oRpts share. You do this by adding a "generic constraint".

In your case I suspect you are writing a website, and so the base class of all your oRpts can be System.Web.UI.Control. If you are not, then work out an appropriate base type (class or interface) for your particular needs.

public static T SetEventHeader<T>(T oRpt , Guid studyPK)
     // Add a "generic constraint" to ensure T is a Control.
     where T : System.Web.UI.Control
{
    var subReport = new XRptEventHeader();
    var eventHeaderList = FreqReports.GetEventHeaderList(studyPK);
    var dataSourceSubReport = (XtraReport)oRpt.FindControl("xrSubreportSite", false);
    dataSourceSubReport.ReportSource = subReport;
    dataSourceSubReport.ReportSource.DataSource = eventHeaderList;
    return oRpt;
}

CodePudding user response：

Thanks to RB as they gave me the information I needed. It also made me realize I needed to cast something else and try/catch for if the section didn't exist for some reason. Here is the final code that worked:

public static T SetEventHeader<T>(T oRpt, Guid studyPK)
        where T : XtraReport
    {
          
        try
        {
            XRSubreport dataSourceSubReport = oRpt.FindControl("xrSubreportSite", false) as XRSubreport;
            var subReport = new XRptEventHeader();
            var eventHeaderList = FreqReports.GetEventHeaderList(studyPK);
            dataSourceSubReport.ReportSource = subReport;
            dataSourceSubReport.ReportSource.DataSource = eventHeaderList;
            return oRpt;
        }
        catch (Exception ex)
        {
            return oRpt; //subsection not present
        }
        
        
    }