my code is
 <CR:CrystalReportViewer ID="CrystalReportViewer1" runat="server" 
                                AutoDataBind="True" DisplayPage="False" 
                                ReportSourceID="CrystalReportSource1" Width="125px" />
                            <CR:CrystalReportSource ID="CrystalReportSource1" runat="server">
                                <Report FileName="Cashvoucher.rpt">
                                </Report>
                            </CR:CrystalReportSource>
my code is
 ReportDocument reportdocument = new ReportDocument();
        string iid = Request.QueryString["id"].ToString();
        reportdocument.Load(Server.MapPath("Cashvoucher.rpt"));
        ParameterFields paramFields = new ParameterFields();
        ParameterField paramField = new ParameterField();
        ParameterDiscreteValue paramDiscreteValue = new ParameterDiscreteValue();
        paramField.Name = "iid";
        paramDiscreteValue.Value = iid;
        paramField.CurrentValues.Add(paramDiscreteValue);
        paramFields.Add(paramField);
        CrystalReportViewer1.ParameterFieldInfo = paramFields;
        // reportdocument.SetParameterValue("id", 3)
        string str = "select id,Name,Section,Details,advance from salary where id='" + iid + "'";
        DataSet ds = mvl.GETDS(str);    
        reportdocument.SetDataSource(ds.Tables[0]);
        CrystalReportViewer1.ReportSource = reportdocument;
        CrystalReportViewer1.RefreshReport();
marvel is my class file