No valid report source is available

Question

Hello There;

I am trying to view my report files on CrystalReport viewer in ASP.NET programmatically. by using the code blow;

            CrystalReportSource reportsource = new CrystalReportSource();
            CrystalDecisions.Web.Report report = new CrystalDecisions.Web.Report();
            Guid reportid = new Guid(Request.QueryString["GUID"]);
            string path = Server.MapPath("/Reports/") + dc.Reports.Where(k => k.OID == reportid).First().FileContent;
            report.FileName = path;
            reportsource.Report = report;
            CrystalReportViewer1.ReportSource = reportsource;

it is working fine it it is a normal basic report, but if it has any group tree or parameter, when I try to expand any node of the group tree, it says No valid report source is available. but if I do it via CrystaReportSource wizard there is no problem at all. what do I miss here? thanks for your help. regards.