A Simple DAL Layer with Transaction support in C#

A Simple DAL layer to access SQL Server with transaction
support.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.SqlClient;

namespace DbLayer
{
   public class TSQLAccess
    {
       
            private SqlConnection _con = null;
            private SqlCommand _cmd = null;
            string _constr;
             SqlTransaction _tran;

       
            public TSQLAccess(string constr)
            {
                _constr = constr;
            }

            public bool Open()
            {
                _con = new SqlConnection(_constr);
                _con.Open();
                _tran = _con.BeginTransaction();
                 return true;
            }

            public bool Close()
            {
                _tran.Commit();
                _con.Close();
                return true;
            }

            public bool Abort()
            {
                _tran.Rollback();
                _con.Close();
                return true;
            }

            public DataSet Execute(string SQL)
            {
                
                _cmd = new SqlCommand(SQL, _con);
                _cmd.Transaction = _tran;
                SqlDataAdapter da = new SqlDataAdapter(_cmd);
                DataSet ds = new DataSet();
                da.Fill(ds);
                
                return ds;
            }

            public SqlDataReader ExecuteQuery(string SQL)
            {
                
                _cmd = new SqlCommand(SQL, _con);
                _cmd.Transaction = _tran;
                SqlDataReader rs = _cmd.ExecuteReader();
                
                return rs;
            }

            public bool ExecuteNonQuery(string SQL)
            {
                try
                {
                    
                    _cmd = new SqlCommand(SQL, _con);
                    _cmd.Transaction = _tran;
                    _cmd.ExecuteNonQuery();
                    
                    return true;
                }
                catch (Exception e)
                {
                    e.ToString();
                    return false;
                }
            }
        }
    }

The usage of the above class is given below

public class Journal
{
        public string jid;
        public string jdate;
        public string narration;
        public List<JournalEntry> rs;

}

public class JournalEntry
{
       public string jcode;
       public string jname;
       public string drcr;
       public string amount;
}


private static bool DoPost(Journal j)
{
    TSQLAccess sq = new TSQLAccess(DbConfig.GetConStr("MAINDB"));
  
    try
    {
       sq.Open();  
       string qry = "insert into JournalMaster values('" + j.jid + "','JV',
       cast('"+DateTime.Now.ToLongDateString()+ "' as datetime),0,'" + j.narration + "')";

       if (!sq.ExecuteNonQuery(qry))
       {
             return false;
       }

       List<JournalEntry> je = j.rs;

       foreach (JournalEntry js in je)
       {
           qry = "insert into JournalDetail values('" + j.jid + "','" + 
           js.jcode + "','" + js.drcr + "'," + js.amount + ")";
           sq.ExecuteNonQuery(qry);
       }
       sq.Close();
       return true;
     }
     catch (Exception ex)
     {
        sq.Abort();
        return false;
     }
}