ASP.NET Optimistic Concurrency Control

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;

namespace Concurrency
{
	/// <summary>
	/// Summary description for _Default.
	/// </summary>
	public class _Default : System.Web.UI.Page
	{
		protected System.Web.UI.WebControls.Label lblCategories;
		protected System.Web.UI.WebControls.DropDownList cmbCategories;
		protected System.Web.UI.WebControls.Table tblProducts;
	
		private void Page_Load(object sender, System.EventArgs e)
		{
			if (! IsPostBack)
			{
				// Lod the categories
				foreach (BLL.Category category in new BLL.Category().GetCategories())
					this.cmbCategories.Items.Add(new ListItem(category.Name, category.ID.ToString()));
				LoadProducts();
			}
		}

		#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.cmbCategories.SelectedIndexChanged += new System.EventHandler(this.cmbCategories_SelectedIndexChanged);
			this.Load += new System.EventHandler(this.Page_Load);

		}
		#endregion

		private void cmbCategories_SelectedIndexChanged(object sender, System.EventArgs e)
		{
			LoadProducts();
		}

		/// <summary>
		/// Loads the products for the selected category
		/// </summary>
		private void LoadProducts()
		{
			TableCell cell;
			TableRow row;
			int rowIndex = 0;
			string url;

			// Get the category ID
			int categoryID = Int32.Parse(cmbCategories.SelectedItem.Value);

			// Load the products asociated to the category
			foreach (BLL.Product product in new BLL.Product().GetProductsByCategory(categoryID))
			{
				row = new TableRow();

				// Set the row style
				rowIndex++;
				if (rowIndex % 2 == 0)
					row.BackColor = Color.White;
				else
					row.BackColor = Color.LightGray;

				// Build the URL to edit the product
				url = "Product.aspx?ProductID=" + product.ID.ToString();
				
				cell = new TableCell();
				cell.Text = "<a href='" + url + "'>Edit</a>";
				row.Cells.Add(cell);

				cell = new TableCell();
				cell.Text = product.Name;
				row.Cells.Add(cell);

				cell = new TableCell();
				cell.Text = product.QuantityPerUnit;
				row.Cells.Add(cell);

				cell = new TableCell();
				cell.Text = product.UnitPrice.ToString();
				row.Cells.Add(cell);

				cell = new TableCell();
				cell.Text = product.UnitsInStock.ToString();
				row.Cells.Add(cell);

				cell = new TableCell();
				cell.Text = product.UnitsOnOrder.ToString();
				row.Cells.Add(cell);

				cell = new TableCell();
				cell.Text = product.ReorderLevel.ToString();
				row.Cells.Add(cell);

				cell = new TableCell();
				if (product.Discontinued)
					cell.Text = "Yes";
				else
					cell.Text = "No";
				row.Cells.Add(cell);

				tblProducts.Rows.Add(row);
			}		
		}

	}
}