setting isolation level

CREATE PROCEDURE [dbo].[MyProc]
        
             (
             @serieType char(2) = null,
             @antall int = 1,
             @firstIdx int = null OUTPUT
             ) 

 SET NOCOUNT ON
 declare @current int, @maks int, @new_current int
 SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
   begin transaction
    SELECT @current = [currentNr] , @maks = [MaxNr]
    FROM [dbo].[SERIE]
     WHERE serieType = @serieType
     if @current is not null
          [some logic]
   commit

 TransactionSettings transactionSettings = // just want to set isolation level
                new TransactionSettings(UseDTCOption.False);
           
            RdbQuery q = new RdbQuery(typeof(NrSerie));
            q.QueryStrategy = new QueryStrategy(QueryStrategy.DataSourceOnly, transactionSettings); 
            q.AddClause(NrSerieDataRow.SerieTypeEntityColumn, EntityQueryOp.EQ, typecode);
            //  --- begin transac. 
            NrSerie serie = pm.GetEntity<NrSerie>(q);
            result = serie.Counter;
            serie.Counter += 1;
           List<IdeaBlade.Persistence.Entity> l = new List<IdeaBlade.Persistence.Entity>(1);
            l.Add(serie);
            SaveResult saveOperation = pm.SaveChanges(l);
            if (!saveOperation.Ok)
            { //roll back
                pm.RejectChanges();//???
                throw saveOperation.Exception;
            }
            //commit

  PersistenceManager manager = new PersistenceManager();
  string keyName = manager.GetDataSourceKey(typeof(MyEntity)).Name; // or "Default"
  string oleDbConnString = RdbKey.LocateRdbKey(keyName).ConnectionString;

using (OleDbConnection sqlConn = new OleDbConnection(oleDbConnString))
{
  OleDbCommand  cmd = new OleDbCommand("Select count(*) from MyTable");
  cmd.Connection = sqlConn;
  sqlConn.Open();
    count = (Int32)(cmd.ExecuteScalar());
  sqlConn.Close();
}