Crystalreport not showing any data and no errors

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C#

ASP.NET

CrystalReports

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?

What I have tried:

Changing the code

protected void btn1_Click(object sender, EventArgs e)
            {
string constring = "Data Source=as400_2;User Id=FADLI;Authentication=Server;Initial Catalog=S065FD45;Network Transport Library=TCPIP;Host CCSID=37;PC Code Page=1252;Network Address=as400.asei.co.id;Network Port=446;Package Collection=FADLI;Default Schema=FADLI;Units of Work=RUW;Default Qualifier=FADLI;DBMS Platform=DB2MVS;Use Early Metadata=False;Defer Prepare=False;Persist Security Info=True;Derive Parameters=True;Pooling=False;Rowset Cache Size=0;DateTime as Char=False;Decimal As Numeric=False;BinaryCodePage=0;Datetime As Date=False;AutoCommit=True;LoadBalancing=False";

SqlConnection con = new SqlConnection(constring);
SqlCommand cmd = new SqlCommand("SELECT COBKD, COBDESC FROM ASEINDTA.MSTCOB", con);

DataTable dt = new DataTable();
SqlDataAdapter adp = new SqlDataAdapter();
adp.SelectCommand = cmd;
adp.Fill(dt);
ReportDocument rptDoc = new ReportDocument();
rptDoc.Load(Server.MapPath("~/test_upload/CrystalReport1.rpt"));
rptDoc.SetDataSource(dt);
CrystalReportViewer1.ReportSource = rptDoc;
CrystalReportViewer1.DataBind();
}