An ADO.NET multi-database, multi-tier solution

using System;
using System.Data;
using System.Data.OleDb;
using System.Globalization;

namespace MultiTier.Data {

	public abstract class OleDBTier : DataTier {

		private OleDbConnection cnConnection;
		private OleDbDataAdapter daDataAdapter;
		
		protected OleDBTier(string connection) : base(connection) {
		}

		protected OleDBTier(string connection, string tableName) : base(connection, tableName) {
		}

		public OleDbConnection Connection {
			get { return cnConnection; }
			set { cnConnection = value; }
		}

		public OleDbDataAdapter DataAdapter {
			get { return daDataAdapter; }
			set { daDataAdapter = value; }
		}

		protected abstract override void ConstructDataAdapter();

		public override DataTable ReadData() {
			/*--- Create a new DataSet ---*/
			this.Table = new DataTable(this.TableName);
			this.Table.Locale = CultureInfo.InvariantCulture;

			try {
				/*--- Fill the DataSet with the Customers ---*/
				this.AffectedRecords = daDataAdapter.Fill(this.Table);
				/*--- Return the DataSet ---*/
				return this.Table;
			}
			catch (OleDbException ex) {
				/*--- An error occurred, so we roll the transaction back ---*/
				this.Exception = ex;
				/*--- Return the DataSet ---*/
				return this.Table;
			}
		}

		public override void SaveData(DataTable dataTable) {
			this.Table = dataTable;
			OleDbTransaction trTransaction = null;

			/*--- Save the data ---*/
			try {
				/*--- Set up the conection manually ---*/
				InitializeConnection();
				cnConnection.Open();
				/*--- Begin a transaction ---*/ 
				trTransaction = cnConnection.BeginTransaction();
				/*--- Make all database changes ---*/
				this.AffectedRecords = daDataAdapter.Update(this.Table);
				/*--- Commit the changes ---*/
				trTransaction.Commit();
			}
			catch (DBConcurrencyException ex) {
				/*--- An error occurred, so we roll the transaction back ---*/
				this.Exception = ex;
				trTransaction.Rollback();
			}
			catch (OleDbException ex) {
				/*--- An error occurred, so we roll the transaction back ---*/
				this.Exception = ex;
				trTransaction.Rollback();
			}
			finally {
				/*--- Close the connection that we manually opened ---*/
				trTransaction = null;
				cnConnection.Close();
				cnConnection = null;
			}
		}

		public override void InitializeConnection() {
			cnConnection = new OleDbConnection(this.ConnectionString);
		}
	}
}