Designing and implementing a versatile data access tier for an ASP.NET application

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using BLT;
using TDS;


namespace DAPrototype
{
	/// <summary>
	/// Summary description for OrderDetail.
	/// </summary>
	public class OrderDetail : System.Web.UI.Page
	{
		protected System.Web.UI.WebControls.Label lbHead;
		protected System.Web.UI.WebControls.Label lbTotal;
		protected System.Web.UI.WebControls.DataGrid dgOrderDetail;
		protected System.Web.UI.WebControls.Label lbRemarks;
		protected System.Web.UI.WebControls.Label lbDelete;
		protected System.Web.UI.WebControls.Button btnDelete;
		protected System.Web.UI.WebControls.HyperLink hlCustomSerch;


		/// <summary>
		/// Sort Expression f�r Datagrid
		/// </summary>
		string strSortExpression;
	
		private void Page_Load(object sender, System.EventArgs e)
		{
			if(!this.IsPostBack)
			{
				 string strOrderID= Request.QueryString["OrderID"];
				 lbHead.Text="Order: "+ strOrderID;
				 this.ViewState["OrderID"] = strOrderID;
				 this.FillDataGrid();	
			}   
		}

		/// <summary>
		/// populate the page controls
		/// </summary>
		void FillDataGrid( )
		{
			try
			{
				if(ViewState["OrderID"]!=null)
				{
					//  Populate the DataGrid
					int nOrderID = Convert.ToInt32(ViewState["OrderID"]);

					BLOrder blOrder  = new BLOrder();
					DSOrderDetail dsOrderDetail = null;
					decimal dTotal;
					blOrder.GetOrderDetail(nOrderID,out dsOrderDetail,out dTotal);

					DataTable dtOrderDetail = dsOrderDetail.OrderDetails;
					DataView dgView = dtOrderDetail.DefaultView;
					if(this.strSortExpression!=null)
					{
					  dgView.Sort= strSortExpression;
					}
					this.dgOrderDetail.DataSource = dgView;
					dgOrderDetail.DataBind();
	        
					/// Display Amount
					lbTotal.Text ="Total Amount: "+dTotal.ToString();
					lbTotal.Visible = true;
	
				 }
			}
			catch(Exception oException)
			{
				string strMessage = oException.Message;
				Exception e = new Exception(strMessage+" FillDataGrid( )");
				this.Context.AddError(e);
			}
				
		}

		#region Web Form Designer generated code
		override protected void OnInit(EventArgs e)
		{
			//
			// CODEGEN: This call is required by the ASP.NET Web Form Designer.
			//
			InitializeComponent();
			base.OnInit(e);
		}
		
		/// <summary>
		/// Required method for Designer support - do not modify
		/// the contents of this method with the code editor.
		/// </summary>
		private void InitializeComponent()
		{    
			this.dgOrderDetail.CancelCommand += new System.Web.UI.WebControls.DataGridCommandEventHandler(this.dgOrderDetail_CancelCommand);
			this.dgOrderDetail.EditCommand += new System.Web.UI.WebControls.DataGridCommandEventHandler(this.dgOrderDetail_EditCommand);
			this.dgOrderDetail.SortCommand += new System.Web.UI.WebControls.DataGridSortCommandEventHandler(this.dgOrderDetail_SortCommand);
			this.dgOrderDetail.UpdateCommand += new System.Web.UI.WebControls.DataGridCommandEventHandler(this.dgOrderDetail_UpdateCommand);
			this.btnDelete.Click += new System.EventHandler(this.btnDelete_Click);
			this.Load += new System.EventHandler(this.Page_Load);

		}
		#endregion

	
		/// <summary>
		/// Callback method for the event dgOrderDetail.SortCommand
		/// </summary>
		/// <param name="source"></param>
		/// <param name="e"></param>
		private void dgOrderDetail_SortCommand(object source,DataGridSortCommandEventArgs e)
		{
		   strSortExpression = e.SortExpression;
		   this.FillDataGrid();
		 
		}

		/// <summary>
		/// Callback method for the event dgOrderDetail.EditCommand
		/// </summary>
		/// <param name="source"></param>
		/// <param name="e"></param>
		private void dgOrderDetail_EditCommand(object source,DataGridCommandEventArgs e)
		{
			  dgOrderDetail.EditItemIndex = e.Item.ItemIndex;
			  this.FillDataGrid();
		}

		/// <summary>
		/// Callback method for the event dgOrderDetail.CancelCommand
		/// </summary>
		/// <param name="source"></param>
		/// <param name="e"></param>
		private void dgOrderDetail_CancelCommand(object source,DataGridCommandEventArgs e)
		{
           
		   dgOrderDetail.EditItemIndex = -1;
		   this.FillDataGrid();
		  
		}

		/// <summary>
		/// Callback method for the event dgOrderDetail.UpdateCommand
		/// </summary>
		/// <param name="source"></param>
		/// <param name="e"></param>
		private void dgOrderDetail_UpdateCommand(object source,DataGridCommandEventArgs e)
		{
			try
			{
			  string strQuantity = ((TextBox)e.Item.Cells[3].Controls[0]).Text;
			  string strProductID = e.Item.Cells[0].Text;
			
			  int nQuantity = Convert.ToInt16(strQuantity);
			  int nProductID = Convert.ToInt16(strProductID);
			  int nOrderID = Convert.ToInt16(ViewState["OrderID"]);

			  BLOrder blOrder = new BLOrder();
			  blOrder.UpdateOrderDetail(nOrderID,nProductID,nQuantity);
			  dgOrderDetail.EditItemIndex = -1;
			  this.FillDataGrid();
			
			}
			catch(Exception oException)
			{
			  string strMessage = oException.Message;
              this.lbRemarks.Text = strMessage;
		
			}
		}

		/// <summary>
		/// Deletes an order with its details
		/// </summary>
		/// <param name="sender"></param>
		/// <param name="e"></param>
		private void btnDelete_Click(object sender, System.EventArgs e)
		{
			try
			{
				if( ViewState["OrderID"] != null)
				{
					int nOrderID = Convert.ToInt32(ViewState["OrderID"]);
					BLOrder blOrder = new BLOrder();
                    bool bDelete = blOrder.DeleteOrder(nOrderID);
					if(bDelete == false)
					{
						lbRemarks.Text = "Delete was unsuccessful";
					}
					else
					{
                        lbRemarks.Text = "Delete was successful";
						btnDelete.Enabled = false;
						this.dgOrderDetail.DataSource = null;
						this.dgOrderDetail.DataBind();
					}
				}
				
			}
			catch(Exception oException)
			{
				string strMessage = oException.Message;
				Exception oExp = new Exception(strMessage+" DeleteOrder");
				this.Context.AddError(oExp);

			}
		
		}
	}
}