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

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

namespace MultiTier.Example.Data {

	public class OrdersOle : MultiTier.Common.OleDBTier {

		public OrdersOle(string connection) : base(connection) {
		}

		public OrdersOle(string connection, string tableName) : base(connection, tableName) {
		}
	
		protected override void ConstructDataAdapter() {
			string strQuery = "";
			OleDbCommand cmSelect;
			OleDbCommand cmUpdate;
			OleDbCommand cmInsert;
			OleDbCommand cmDelete;

			//--- Set up the Connection
			InitializeConnection();

			//--- Set up the SELECT Command
			strQuery = @"SELECT OrderID, CustomerID, OrderDate, RequiredDate, ShippedDate, Freight
						 FROM Orders";
			cmSelect = null;
			cmSelect = new OleDbCommand(strQuery, this.Connection);
			cmSelect.CommandType = CommandType.Text;

			//--- Set up the UPDATE Command
			strQuery = @"UPDATE Orders
						 SET CustomerID = @CustomerID , OrderDate = @OrderDate, RequiredDate = @RequiredDate, ShippedDate = @ShippedDate, Freight = @Freight
						 WHERE OrderID = @OrderID";
			cmUpdate = null;
			cmUpdate = new OleDbCommand(strQuery, this.Connection);
			cmUpdate.CommandType = CommandType.Text;
			cmUpdate.Parameters.Add(new OleDbParameter("@CustomerID", OleDbType.WChar, 5, "CustomerID"));
			cmUpdate.Parameters.Add(new OleDbParameter("@OrderDate", OleDbType.DBTimeStamp, 14, "OrderDate"));
			cmUpdate.Parameters.Add(new OleDbParameter("@RequiredDate", OleDbType.DBTimeStamp, 14, "RequiredDate"));
			cmUpdate.Parameters.Add(new OleDbParameter("@ShippedDate", OleDbType.DBTimeStamp, 14, "ShippedDate"));
			cmUpdate.Parameters.Add(new OleDbParameter("@Freight", OleDbType.Currency, 16, "Freight"));
			cmUpdate.Parameters.Add(new OleDbParameter("@OrderID", OleDbType.Integer, 4, "OrderID"));

			//--- Set up the INSERT Command
			strQuery = @"INSERT INTO Customers (CustomerID, OrderDate, RequiredDate, ShippedDate, Freight)
						 VALUES (@CustomerID, @OrderDate, @RequiredDate, @ShippedDate, @Freight)";
			cmInsert = null;
			cmInsert = new OleDbCommand(strQuery, this.Connection);
			cmInsert.CommandType = CommandType.Text;
			cmInsert.Parameters.Add(new OleDbParameter("@CustomerID", OleDbType.WChar, 5, "CustomerID"));
			cmInsert.Parameters.Add(new OleDbParameter("@OrderDate", OleDbType.DBTimeStamp, 14, "OrderDate"));
			cmInsert.Parameters.Add(new OleDbParameter("@RequiredDate", OleDbType.DBTimeStamp, 14, "RequiredDate"));
			cmInsert.Parameters.Add(new OleDbParameter("@ShippedDate", OleDbType.DBTimeStamp, 14, "ShippedDate"));
			cmInsert.Parameters.Add(new OleDbParameter("@Freight", OleDbType.Currency, 16, "Freight"));

			//--- Set up the DELETE Command
			strQuery = @"DELETE FROM Orders
						 WHERE OrderID = @OrderID";
			cmDelete = null;
			cmDelete = new OleDbCommand(strQuery, this.Connection);
			cmDelete.CommandType = CommandType.Text;
			cmDelete.Parameters.Add(new OleDbParameter("@OrderID", OleDbType.Integer, 4, "OrderID"));
			//---------------------------------------------------------
			//--- Create and set up the DataAdapter
			//---------------------------------------------------------
			this.DataAdapter = new OleDbDataAdapter();
			this.DataAdapter.SelectCommand = cmSelect;
			this.DataAdapter.UpdateCommand = cmUpdate;
			this.DataAdapter.InsertCommand = cmInsert;
			this.DataAdapter.DeleteCommand = cmDelete;
			
			//--- Destroy connection object
			this.Connection = null;
		}
	}
}