Data is Null. This method or property cannot be called on Null values.

Hi,
Iam trying to fetch data from database(sql server) based on a month,year and id.
My storedprocedure is as follows:-

SELECT SUM(kWDiff),SUM(kVADiff)from dbo.Socket_Final_Insert_Meter_Detail where((datepart(MM, Reading_Date)=@month and datepart(YYYY, Reading_Date)=@year)and(datepart(HH, Reading_Date)between 22 and 06)and Meter_Number=@meterid AND (datepart(HH, Reading_Date)IS NULL))

And my c# code for calling the SP is:-

#region OffPeakkVA_kW
       public Invoice OffPeakkVA_kW(int Meter_Number, int month, int year)
       {
           try
           {
               Invoice invoice = new Invoice();


               SqlDataReader rdr = null;
               _sqlConnection.Open();
               SqlCommand sql_Cmd = new SqlCommand("Off_peak_kva_kw_calculation", _sqlConnection);
               sql_Cmd.CommandType = CommandType.StoredProcedure;
               sql_Cmd.Parameters.Add(new SqlParameter("@meterid", Meter_Number));
               sql_Cmd.Parameters.Add(new SqlParameter("@month", month));
               sql_Cmd.Parameters.Add(new SqlParameter("@year", year));

               rdr = sql_Cmd.ExecuteReader();
               //int count = rdr.FieldCount;

               while (rdr.Read())
               {

                   invoice.KW_offpeak = rdr.GetDouble(0);
                   invoice.KVA_offpeak = rdr.GetDouble(1);

               }
               sql_Cmd.Dispose();
               _sqlConnection.Close();
               return invoice;

           }
           catch (Exception ex)
           {

               throw ex;
           }
       }
       #endregion

But while executing it is throwing exception 'Data is Null. This method or property cannot be called on Null values.'.But my databse contains sufficient values,still it is throwing the exception.How to resolve this issue?

Tags: C#