cannot convert from 'Microsoft.Xrm.Sdk.Query.QueryExpression' to 'Microsoft.Crm.Sdk.Query.QueryBase

Hi am getting the above error with the below code..i read somewhere that said i should remove all references to Microsoft.Crm.Sdk.dll but that didnt work..please assist if you can

using System;

using System.Collections.Generic;

using Microsoft.Xrm.Sdk;

using InvoiceMVCApp.Models;

using Microsoft.Xrm.Sdk.Query;

using Microsoft.Xrm.Client.Services;

using Microsoft.Xrm.Client;

namespace InvoiceMVCApp.DAL {

publicclass DAL_InvoicesEntity
{publicList<InvoicesModel>RetriveRecords(){var connection =newCrmConnection("Server=CRM Online");
        using (OrganizationService service =newOrganizationService("ConnectionString", connection)){QueryExpression query =newQueryExpression{EntityName="invoice",ColumnSet=newColumnSet("invoiceid","customer","invoicename","paymentreceived","commission","adminfee","discountamount")};List<InvoicesModel> info =newList<InvoicesModel>();EntityCollection invoiceRecord = service.RetrieveMultiple(query);if(invoiceRecord !=null&& invoiceRecord.Entities.Count>0){InvoicesModel invoiceModel;for(int i =0; i < invoiceRecord.Entities.Count; i++){
                    invoiceModel =newInvoicesModel();if(invoiceRecord[i].Contains("invoiceid")&& invoiceRecord[i]["invoiceid"]!=null)
                        invoiceModel.InvoiceID=(Guid)invoiceRecord[i]["invoiceid"];if(invoiceRecord[i].Contains("customer")&& invoiceRecord[i]["customer"]!=null)
                        invoiceModel.ClientName=((EntityReference)invoiceRecord[i]["customer"]);if(invoiceRecord[i].Contains("invoiceid")&& invoiceRecord[i]["invoiceid"]!=null)
                        invoiceModel.InvoiceNumber= invoiceRecord[i]["invoiceid"].ToString();if(invoiceRecord[i].Contains("commission")&& invoiceRecord[i]["commission"]!=null)
                        invoiceModel.Commission=(decimal)(invoiceRecord[i]["commission"]);if(invoiceRecord[i].Contains("adminfee")&& invoiceRecord[i]["adminfee"]!=null)
                        invoiceModel.AdminFee=(decimal)invoiceRecord[i]["adminfee"];if(invoiceRecord[i].Contains("discountamount")&& invoiceRecord[i]["discountamount"]!=null)
                        invoiceModel.Discount=((decimal)invoiceRecord[i]["discountamount"]);
                    info.Add(invoiceModel);}}return info;}}}

}