Enterprise Library 4.1学习---缓存应用程序块-原创手记-慕课网

缓存是个啥？以及为啥要用缓存就不废话了，主要是从实用角度讲下怎么用

1.先添加对Microsoft.Practices.EnterpriseLibrary.Caching.dll的引用

2.修改web.config文件,注意高度部分

<configSections>
...
<section name="cachingConfiguration" type="Microsoft.Practices.EnterpriseLibrary.Caching.Configuration.CacheManagerSettings, Microsoft.Practices.EnterpriseLibrary.Caching, Version=4.1.0.0, Culture=neutral" />
...

</configSections>
<cachingConfiguration defaultCacheManager="Cache Manager">
    <cacheManagers>
      <add expirationPollFrequencyInSeconds="60" maximumElementsInCacheBeforeScavenging="1000"
        numberToRemoveWhenScavenging="10" backingStoreName="Null Storage"
        type="Microsoft.Practices.EnterpriseLibrary.Caching.CacheManager, Microsoft.Practices.EnterpriseLibrary.Caching, Version=4.1.0.0, Culture=neutral"
        name="Cache Manager" />
    </cacheManagers>
    <backingStores>
      <add encryptionProviderName="" type="Microsoft.Practices.EnterpriseLibrary.Caching.BackingStoreImplementations.NullBackingStore, Microsoft.Practices.EnterpriseLibrary.Caching, Version=4.1.0.0, Culture=neutral"
        name="Null Storage" />
    </backingStores>
</cachingConfiguration>
...

3.使用缓存，见下面的代码，关键地方都加了注释

复制代码 using System;
using System.Collections.Generic;
using Microsoft.Practices.EnterpriseLibrary.Caching;
using Microsoft.Practices.EnterpriseLibrary.Caching.Expirations;

namespace CacheTest
{
    /// <summary>
    /// 定义要缓存的实体类
    /// </summary>
    public class MyData
    {
        public string Name { set; get; }
        public int Age { set; get; }
        public string Color { set; get; }
    }

    public partial class _Default : System.Web.UI.Page
    {
        const string KEYNAME = "myDate";//缓存的键值

        ICacheManager cacheManager;

        protected void Page_Load(object sender, EventArgs e)
        {
            cacheManager = CacheFactory.GetCacheManager();//实例化ICachemanager
        }

        protected void btnWrite_Click(object sender, EventArgs e)
        {
            //生成要缓存的数据(实际开发中可以是从数据库查询出来的数据)
            List<MyData> _list = new List<MyData>{
                new MyData(){ Age=1, Color="Yellow", Name="China"},
                new MyData{ Age=2,Color="Black",Name="USA"}
            };

            AbsoluteTime _ExpireTime = new AbsoluteTime(DateTime.Now.AddSeconds(30));//指定30秒后过期

            cacheManager.Add(KEYNAME, _list, CacheItemPriority.Normal, null, _ExpireTime);//加入缓存

            Response.Write("Cache写入完成," + DateTime.Now.ToString());
        }

        protected void btnRead_Click(object sender, EventArgs e)
        {

            this.R1.DataSource = GetCacheData();
            this.R1.DataBind();
            Response.Write("Cache加载完成," + DateTime.Now.ToString());

        }

        /// <summary>
        /// 获取缓存数据
        /// </summary>
        /// <returns></returns>
        public List<MyData> GetCacheData()
        {
            List<MyData> _cacheData = cacheManager.GetData(KEYNAME) as List<MyData>;

            if (null == _cacheData)//记得一定要加此判断(因为缓存可能过期)
            {
                //如果缓存数据为空，则重新生成数据，并加入缓存(为检测效果，特地把Color与Name前加了一个"New")
                _cacheData = new List<MyData>{
                new MyData(){ Age=1, Color="New Yellow", Name="New China"},
                new MyData{ Age=2,Color="New Black",Name="New USA"}
                };

                AbsoluteTime _ExpireTime = new AbsoluteTime(DateTime.Now.AddSeconds(30));//指定30秒后过期

                cacheManager.Add(KEYNAME, _cacheData, CacheItemPriority.Normal, null, _ExpireTime);
            }

            return _cacheData;
        }

    }
}
复制代码前端页面很简单
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="CacheTest._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <asp:Button ID="btnWrite" runat="server" Text="Write Cache" OnClick="btnWrite_Click" />
    <asp:Button ID="btnRead" runat="server" Text="Load Cache"
        onclick="btnRead_Click" />
    <asp:Repeater ID="R1" runat="server" EnableViewState="false">
        <HeaderTemplate>
            <ul>
        </HeaderTemplate>
        <ItemTemplate>
            <li>Age：<%# Eval("Age") %>，Name：<%# Eval("Name")%>，Color：<%# Eval("Color")%></li>
        </ItemTemplate>
        <FooterTemplate>
            </ul>
        </FooterTemplate>
    </asp:Repeater>
    </form>
</body>
</html> 复制代码
值得一提的是，缓存是"全局"性质的，也就是说在一个页面写入了缓存，另一个页面也可以读取（当然:前提是缓存未过期的情况下），我们可以利用这个特性把网站中经常使用的数据(比如一些基础数据)缓存起来，其它要用的地方直接从缓存读取，能有效减少对数据库的访问。