Passing Parameter to Crystal Report

   ReportDocument report_crp;
    CrystalReportViewer crv;

crv = new CrystalReportViewer();
            report_crp = new ReportDocument();
            report_crp.Load(Server.MapPath("reportname"));
            #region Parameters passing to rpt file
            //  Passing parametrs
            ParameterValues pvs = new ParameterValues();
            ParameterDiscreteValue pdsv = new ParameterDiscreteValue();
            ParameterFieldDefinitions pfds;
            ParameterFieldDefinition pfd;

            pfds = report_crp.DataDefinition.ParameterFields;
            pfd = pfds["@Param1"];
            pvs = pfd.CurrentValues;
            pdsv = new ParameterDiscreteValue();
            pdsv.Value = Request.QueryString["Param1"].ToString();// "11/06/2010";
            pvs.Add(pdsv);
            pfd.ApplyCurrentValues(pvs);

            pfds = report_crp.DataDefinition.ParameterFields;
            pfd = pfds["@Param2"];
            pvs = pfd.CurrentValues;
            pdsv = new ParameterDiscreteValue();
            pdsv.Value = Request.QueryString["Param2"].ToString();//"7373";
            pvs.Add(pdsv);
            pfd.ApplyCurrentValues(pvs);

            pfds = report_crp.DataDefinition.ParameterFields;
            pfd = pfds["@Param3"];
            pvs = pfd.CurrentValues;
            pdsv = new ParameterDiscreteValue();
            pdsv.Value = Request.QueryString["Param3"].ToString();//"M01";
            pvs.Add(pdsv);
            pfd.ApplyCurrentValues(pvs);

            //End Passing paramentes
            #endregion
            crv.ReportSource = report_crp;
            crv.HasExportButton = true;
            crv.HasToggleGroupTreeButton = true;
            crv.DisplayGroupTree = true;
            crv.HasCrystalLogo = true;
            crv.HasDrillUpButton = true;
            crv.HasViewList = true;
            crv.HasPrintButton = true;