周期性的查询数据库(基于购物车).txt

C# 是创新性的新式编程语言

对于数据库内容不是经常变化的，下面的做法更高效

1.周期性的查询数据库，在应用程序中保存结果，在应用程序缓存中保存结果，并用缓存中的数据填充DataGrid

1.WebForm1.aspx.cs

private void Page_Load(object sender, System.EventArgs e)
		{
			DataSet ds = (DataSet)Cache["titles"];

			if (ds != null) 
			{
				DataGrid1.DataSource=ds;
				DataGrid1.DataBind();				
			}
			else 
			{
				Label1.Text = "Server busy";
			}

		}
2.Global.asax.cs
using System;
using System.Collections;
using System.ComponentModel;
using System.Web;
using System.Web.SessionState;
using System.Web.Caching;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
namespace MyCongo 
{
	/// <summary>
	/// Global 的摘要说明。
	/// </summary>
	public class Global : System.Web.HttpApplication
	{
		/// <summary>
		/// 必需的设计器变量。
		/// </summary>
		private System.ComponentModel.IContainer components = null;

		static Cache _cache = null;


		public Global()
		{
			InitializeComponent();
		}	
		
		protected void Application_Start(Object sender, EventArgs e)
		{
			_cache = Context.Cache;

			DataSet ds=ReadDataSet();

			if (ds != null) 
			{
				//将数据集插入缓存中
				_cache.Insert ("titles", ds, null,
					Cache.NoAbsoluteExpiration, TimeSpan.FromMinutes(5),
					CacheItemPriority.AboveNormal,
					new CacheItemRemovedCallback(RefreshDS));
			}
		}
		//回调函数
		static void RefreshDS (String key, Object item,
			CacheItemRemovedReason reason)
		{
			
			DataSet ds=ReadDataSet();
			if (ds != null) 
			{
				_cache.Insert ("titles", ds, null,
					Cache.NoAbsoluteExpiration, TimeSpan.FromMinutes(5),
					CacheItemPriority.AboveNormal,
					new CacheItemRemovedCallback(RefreshDS));
			}
		}

		static DataSet ReadDataSet ()
		{
			string ConnectString =
				ConfigurationSettings.AppSettings["connectString"];
			SqlDataAdapter adapter = new SqlDataAdapter
				("select * from titles where price != 0", ConnectString);
			DataSet ds = new DataSet ();
			adapter.Fill (ds);
			return ds;
		}

 
		protected void Session_Start(Object sender, EventArgs e)
		{
				Session["MyShoppingCart"] = new ShoppingCart();
		}

		protected void Application_BeginRequest(Object sender, EventArgs e)
		{

		}

		protected void Application_EndRequest(Object sender, EventArgs e)
		{

		}

		protected void Application_AuthenticateRequest(Object sender, EventArgs e)
		{

		}

		protected void Application_Error(Object sender, EventArgs e)
		{

		}

		protected void Session_End(Object sender, EventArgs e)
		{

		}

		protected void Application_End(Object sender, EventArgs e)
		{

		}
			
		#region Web 窗体设计器生成的代码
		/// <summary>
		/// 设计器支持所需的方法 - 不要使用代码编辑器修改
		/// 此方法的内容。
		/// </summary>
		private void InitializeComponent()
		{    
			this.components = new System.ComponentModel.Container();
		}
		#endregion
	}
}