[Solved] ASP.Net Crystal Report Preview Error: Object reference not set to an instance of an object in IIS

I am facing error in Crystal Report Preview.

error: Object reference not set to an instance of an object

It is working fine on local machine but not working on server side.

C#

SqlConnection con = new SqlConnection();
ReportDocument rpt = new ReportDocument();
protected void Page_Load(object sender, EventArgs e)
{
    //if (!IsPostBack)
    {
        rpt.Dispose();
        rpt.Close();
        loadReport();
    }
}
private void loadReport()
{
    rpt.Dispose();
    rpt.Close();
    con = new SqlConnection("Data Source=SERVER1\\SQLEXPRESS;Integrated Security=SSPI;Initial Catalog=ucms;MultipleActiveResultSets=True;");

    try
    {
        con.Open();
        SqlCommand cmd = new SqlCommand("sp_bigbaleprint", con);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.AddWithValue("@BID", Request.QueryString["BID"]);
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);

        rpt.Load(Server.MapPath("~/CRBB.rpt"));
        rpt.SetDataSource(ds.Tables["Table"]);
        BBPViewer.ReportSource = rpt;
        rpt.ExportToHttpResponse(CrystalDecisions.Shared.ExportFormatType.PortableDocFormat, Response, false, "Bigbalprd");
    }

    catch (Exception ex)
    {
        rpt.Close();
        rpt.Dispose();
        con.Close();
    }
}
protected void CRBigview_Unload(object sender, EventArgs e)
{
    if (rpt != null)
    {
        rpt.Close();
        rpt.Dispose();
    }
}