【IT168 技术文档】

    虽然现在已经是宽带时代，小猫已经离我们渐渐远去，可作为WEB应用开发者来说，我们仍然有责任和义务不断地通过技术手段来优化WEB应用性能，让用户浏览时少一些等待，多一些爽快。

    所幸的是，ASP.NET作为基于.Net Framework的WEB开发技术，它也享用着.Net Framework的优越性，.Net Framework为我们提供了良好的Cache技术，使我们能开发出速度更快、用户体验更好的WEB应用。命名空间System.Web.Caching提供了Cache类，其Cache的有效性依赖分以下三种情况：
    1． 时间点（指定时间点内有效）；
    2． KEY值（KEY值作Cache项标识）；
    3． 文件或目录（指定文件或目录变更，则原Cache项不可用）；

    下面我就结合实际开发的应用跟大家分享一下使用Cache来提高ASP.NET应用的性能。

    我们在开发中常常会遇到读取记录列表（例如最近更新的新闻列表Top N）、记录本身（例如一条新闻），用户访问的时候，这样的信息是否每次都要重复从数据库中读取呢？聪明的你可能知道，这完全是没必要的。

    我们为了方便处理，不防设计一个SiteCache类（借鉴了CS中的CSCache.cs），并提供若干静态方法，来负责处理Cache项的添加和删除。下面给出类图：

    代码： SiteCache.cs

代码#region 代码
using System;
using System.Collections;
using System.Text.RegularExpressions;
using System.Web;
using System.Web.Caching;
namespace Ycweb.Components
......{
public class SiteCache
 ......{
 private static readonly Cache _cache;
 public static readonly int DayFactor;
 private static int Factor;
 public static readonly int HourFactor;
 public static readonly int MinuteFactor;
 static SiteCache()
......{
 DayFactor = 17280;
 HourFactor = 720;
 MinuteFactor = 12;
 Factor = 5;
 _cache = HttpRuntime.Cache;
 }
 private SiteCache()
 ......{
 }
 public static void Clear()
 ......{
 IDictionaryEnumerator enumerator = _cache.GetEnumerator();
 while (enumerator.MoveNext())
 ......{
 _cache.Remove(enumerator.Key.ToString());
 }
 }

 public static object Get(string key)
 ......{
 return _cache[key];
 }

 public static void Insert(string key, object obj)
 ......{
 Insert(key, obj, null, 1);
 }
 public static void Insert(string key, object obj, int seconds)
......{
 Insert(key, obj, null, seconds);
 }

 public static void Insert(string key, object obj, CacheDependency dep)
 ......{
 Insert(key, obj, dep, HourFactor*12);
 }

 public static void Insert(string key, object obj, int seconds, CacheItemPriority priority)
 ......{
 Insert(key, obj, null, seconds, priority);
 }
 public static void Insert(string key, object obj, CacheDependency dep, int seconds)
 ......{
 Insert(key, obj, dep, seconds, CacheItemPriority.Normal);
 }

 public static void Insert(string key, object obj, CacheDependency dep, int seconds, CacheItemPriority priority)
 ......{
 if (obj != null)
 ......{
 _cache.Insert(key, obj, dep, DateTime.Now.AddSeconds((double) (Factor*seconds)), TimeSpan.Zero, priority, null);
 }
 }
 public static void Max(string key, object obj)
 ......{
 Max(key, obj, null);
 }
 public static void Max(string key, object obj, CacheDependency dep)
 ......{
 if (obj != null)
 ......{
 _cache.Insert(key, obj, dep, DateTime.MaxValue, TimeSpan.Zero, CacheItemPriority.AboveNormal, null);
 }
 }
 public static void MicroInsert(string key, object obj, int secondFactor)
 ......{
 if (obj != null)
 ......{
 _cache.Insert(key, obj, null, DateTime.Now.AddSeconds((double) (Factor*secondFactor)), TimeSpan.Zero);
 }
 }
 public static void Remove(string key)
 ......{
 _cache.Remove(key);
 }
 public static void RemoveByPattern(string pattern)
 ......{
 IDictionaryEnumerator enumerator = _cache.GetEnumerator();
 Regex regex1 = new Regex(pattern, RegexOptions.Singleline | RegexOptions.Compiled | RegexOptions.IgnoreCase);
 while (enumerator.MoveNext())
 ......{
 if (regex1.IsMatch(enumerator.Key.ToString()))
 ......{
 _cache.Remove(enumerator.Key.ToString());
 }
 }
 }

 public static void ReSetFactor(int cacheFactor)
 ......{
 Factor = cacheFactor;
 }
 }
}
#endregion

public static RecordSet GetNewsSetTopN(string classCode,int topN,SortPostsBy orderBy, SortOrder sortOrder, string language)
...{
 string cacheKey = string.Format("NewsSetTopN-LG:{0}:CC:{1}:TN:{2}:OB:{3}:SO:{4}", language,classCode,topN.ToString(), orderBy.ToString(),sortOrder.ToString());

 //从上下文中读缓存项 
 RecordSet newsSet = HttpContext.Current.Items[cacheKey] as RecordSet;
 if (newsSet == null)
 ...{
 //从HttpRuntime.Cache读缓存项 
 newsSet = SiteCache.Get(cacheKey) as RecordSet;
 if (newsSet == null)
 ...{
 //直接从数据库从读取 
 CommonDataProvider dp=CommonDataProvider.Instance();
 newsSet =dp.GetNewsSetTopN(language,classCode,topN,orderBy,sortOrder);
 //并将结果缓存到HttpRuntime.Cache中 
 SiteCache.Insert(cacheKey, newsSet, 60, CacheItemPriority.Normal);
 }

 }
return newsSet;
} 

/**//**//**//// <summary>
/// 删除匹配的NewsSetTopN列表的Cache项
/// </summary> 
public static void ClearNewsSetTopNCache(string language,string classCode,int topN)
...{
 string cacheKey = string.Format("NewsSetTopN-LG:{0}:CC:{1}:TN:{2}",language,classCode,topN.ToString());
 SiteCache.RemoveByPattern(cacheKey);
} 

/**//**//**//// <summary>
/// 发布(新建)新闻
/// </summary>
/// <param name="post">新闻实例</param>
/// <returns>返回状态</returns> 
public static int Create(News post)
...{
 int status;
 CommonDataProvider dp=CommonDataProvider.Instance();
 dp.CreateUpdateDeleteNews(post, DataAction.Create, out status);
 //强制清除匹配的缓存项 
 ClearNewsSetTopNCache (post.Language, post.ClassCode,Globals.GetSiteSetting.NewsListTopN);
 return status;
}