How can I encapsulate the data source in a linq query?

try
{
   #region Try to find the Order info in planned orders.
   dcReplication dc = new dcReplication(String.Format(
      "Data Source={0};Initial Catalog={1};User ID={2};Password={3}",
                                        replicationServer,
                                        replicationDatabase,
                                        replicationUsername,
                                        replicationPassword));

   // Find the Bill To and Ship To Customer Numbers in the
   //Sales Order Master table.
   var q1 = (from a in dc.SalesOrderMasterTable
            where a.SalesOrderNumber == orderNumber
            select new { a.BillToCustomerNumber,
                         a.ShipToCustomerNumber }).ToList();

   foreach (var r in q1)
   {  shipToCustomerNumber = r.ShipToCustomerNumber;
      billToCustomerNumber = r.BillToCustomerNumber;
   }

   if (q1.Count > 0)
   {  whereFound = "Planned";
      return orderNumber;
   }
   #endregion
   else
   {
      try
      #region Try to find Order in packed orders.
      {  var q2 = (from a in dc.InvoiceHistoryTable
                   where a.OrderNumber == orderNumber
                   select new { a.BillToCustomerNumber ,
                                a.ShipToCustomerNumber }).Distinct()
                                .ToList();

         foreach (var r in q2)
         {  shipToCustomerNumber = r.ShipToCustomerNumber;
            billToCustomerNumber = r.BillToCustomerNumber;
         }

         if (q2.Count > 0)
         {  whereFound = "Packed";
            return orderNumber;
         }
         else
         {  throw new RowNotInTableException(String.Format
            ("Are you sure you entered the Order Number correctly?  Order '{0}' could not be found in Sales Order Master or Invoice History.",
                                             orderNumber));
         }
      }
      #endregion