service endpoint error

public List<datalist7> getleger(string accno, string fromdate, string todate)
{
   SqlConnection con = new SqlConnection(@"Data Source=saba-PC;Initial Catalog=bcounts;Integrated Security=True");
   con.Open();
   SqlCommand cmd = new SqlCommand("select gt.Value_Date,gt.Voucher_no+'-'+gr.VchrType as voucher,gt.Acct_Nirration,gr.InstrumentNo,gt.Dr_Amount,gt.Cr_Amount  from gl_transaction gt, Gl_Ref gr where gt.Accountno = '" + accno + "'  and gt.Voucher_No=gr.Voucher_no  and gt.Value_Date between '" + fromdate + "' and '" + todate + "'", con);
   SqlDataReader rdr = cmd.ExecuteReader();
   decimal crsum = 0;
   decimal drsum = 0;
   decimal balance = 0;
   List<datalist7> data = new List<datalist7>();
   if (rdr.HasRows)
   {
      while (rdr.Read())
      {
         if (rdr.GetDecimal(4) > 0)
         {
            balance = balance + rdr.GetDecimal(4);
            drsum += rdr.GetDecimal(4);
            data.Add(new datalist7(rdr.GetDateTime(0).ToShortDateString(), rdr.GetString(1), rdr.GetString(2), rdr.GetString(3), rdr.GetDecimal(4).ToString(), "-", balance.ToString()));
         }
         else
         {
            balance = balance - rdr.GetDecimal(5);
            crsum += rdr.GetDecimal(5);
            data.Add(new datalist7(rdr.GetDateTime(0).ToShortDateString(), rdr.GetString(1), rdr.GetString(2), rdr.GetString(3), "-", rdr.GetDecimal(5).ToString(), balance.ToString()));
         }
      }
      data.Add(new datalist7("-", "-", "-", "-", drsum.ToString(), crsum.ToString(), "-"));
   }

   con.Close();
   return data;
}

[OperationContract]
   [WebInvoke(Method = "GET", ResponseFormat = WebMessageFormat.Json,
      BodyStyle = WebMessageBodyStyle.Wrapped,
      UriTemplate = "getleger/accno={accno}&fromdate={fromdate}&todate={todate}")]
      List<datalist7> getleger(string accno, string fromdate, string todate);

http://localhost:49609/ipadservice.svc/getleger/0010010010006/2013-02-01/2014-02-01