Crystal report binding error

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;
using CrystalDecisions.CrystalReports.Engine;
namespace ReportViewer
{
    public partial class _Default : System.Web.UI.Page
    {
        string connStr = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
        SqlDataAdapter sqlda = new SqlDataAdapter();
        SqlCommand com = new SqlCommand();
        DataTable dt;
        DataSet1 ds=new DataSet1();
        ReportDocument rptDoc=new ReportDocument();

        protected void Page_Load(object sender, EventArgs e)
        {
            bindReport();

        }
        private void bindReport()
        {
           
            SqlConnection conn = new SqlConnection(connStr);
            dt = new DataTable();
            dt.TableName = "Crystal Report Example";
            com.Connection = conn;
            com.CommandText = "SELECT * FROM product";
            sqlda = new SqlDataAdapter(com);
            sqlda.Fill(dt);
            ds.Tables[0].Merge(dt);
            rptDoc.Load(Server.MapPath("CrystalReport1.rpt"));
            rptDoc.SetDataSource(ds);
            CrystalReportViewer1.ReportSource = rptDoc;

        }
    }
}