CrystalReport Not showing any data and no errors

Hi, I'm using CrystalReport in my web application. I'm using VS2013. my problem is after adding CrystalReportViewer and CrystalReportSource from tool box and wrote following code in button_click event

protected void btn1_Click(object sender, EventArgs e)
        {
            ReportDocument rptDoc = new ReportDocument();
            rptDoc.Load(Server.MapPath("~/test_upload/CrystalReport1.rpt"));
            CrystalReportViewer1.ReportSource = rptDoc;
            CrystalReportViewer1.DataBind();
        }

it is not showing crystalreport or any data in browser. and not showing any error. How do I solve this?