error in code for crystal report in vs 2010

Question

i am using below code

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Data;

using System.Data.SqlClient;

using System.Configuration;

using System.Configuration;

using CrystalDecisions.CrystalReports.Engine;

using CrystalDecisions.Shared;

using System.IO;

public partial class _Default : System.Web.UI.Page

{

    conn ObjConn = new conn();

    protected void Page_Load(object sender, EventArgs e)

    {

      

       

    }

    protected void Button1_Click(object sender, EventArgs e)

    {

        DataTable dt = new DataTable();

        string str = "select * from Register";

        dt = ObjConn.GetDataTable(str);

        DataSet ds = new DataSet("table");

        ds.Tables.Add(dt);

        ReportViewer1.Visible = true;

        ReportDocument rDoc = new ReportDocument();

        dt.TableName = "Crystal Report ";  // Crystal Report Name

        rDoc.Load(Server.MapPath("userrpt.rpt")); // Your .rpt file path

        rDoc.SetDataSource(ds); //set dataset to the report viewer.

        ReportViewer1.ReportSource = rDoc;   // which  name space i have to use for this 

    }

}