企业库缓存依赖的实现-基于文件依赖_private readonly icachemanager cachemanager = cach-优快云博客

本文介绍了一种基于Microsoft Enterprise Library Caching实现的缓存依赖和到期机制。通过定义CacheItemDependency类实现了缓存项依赖的功能，当指定的缓存项发生变化时，依赖于它的缓存也会自动失效。此外还提供了更新依赖缓存的方法，并附带测试代码验证其有效性。

step1 实现缓存到期接口

using System; using System.Web; using Microsoft.Practices.EnterpriseLibrary.Caching; /// <summary> ///CacheItemDependency 的摘要说明 /// </summary> public class CacheItemDependency : ICacheItemExpiration { //依赖缓存项键 private readonly string dependencyCacheKey; //依赖缓存项值 private System.Int32 lastCount; #region Constructor /// <summary> /// 初始化依赖缓存项，如果此缓存管理对象存在，则取出缓存的数据；若不存在，就要对此缓存管理赋值 /// </summary> /// <param name="cacheKey">依赖缓存项的键</param> public CacheItemDependency(string cacheKey) { dependencyCacheKey = cacheKey; ICacheManager cacheManager = CacheFactory.GetCacheManager(); lastCount = Int32.MinValue; if (cacheManager != null) { if (cacheManager.Contains(cacheKey)) { object o = cacheManager.GetData(cacheKey); if (o != null) { this.lastCount = (int)o; } lastCount = (int)cacheManager.GetData(cacheKey); } else { cacheManager.Add(cacheKey, lastCount); } } } #endregion #region Properties public string DependencyCacheKey { get { return dependencyCacheKey; } } public System.Int32 LastCount { get { return lastCount; } } #endregion #region ICacheItemExpiration Members public bool HasExpired() { ICacheManager cacheManager = CacheFactory.GetCacheManager(); if (cacheManager == null) { return true; } System.Int32 currentCount = (int)cacheManager.GetData(dependencyCacheKey); if (currentCount != lastCount) { return true; } else { return false; } } public void Notify() { } public void Initialize(CacheItem owningCacheItem) { } #endregion }

step2 定义修改依赖项缓存的方法

using System; using System.Web; using Microsoft.Practices.EnterpriseLibrary.Caching; /// <summary> ///DataAccessUtil 的摘要说明 /// </summary> public class DataAccessUtil { public DataAccessUtil() { // //TODO: 在此处添加构造函数逻辑 // } /// <summary> /// 更新所有以cacheKeys中元素为key的缓存项 /// </summary> /// <param name="cacheKeys">缓存项的key的数组</param> public static void UpdateCacheDependency(string[] cacheKeys) { ICacheManager cacheManager = CacheFactory.GetCacheManager(); foreach (string cacheKey in cacheKeys) { if (cacheManager != null && cacheManager.Contains(cacheKey)) { int lastCount = (int)cacheManager.GetData(cacheKey); if (lastCount < Int32.MaxValue) { lastCount++; } else { lastCount = Int32.MinValue; } // 这一句的作用在于更新以cacheKey为key的缓存项,从而使依赖于此缓存项的缓存项失效. cacheManager.Add(cacheKey, lastCount); } } } }

step3 测试代码

using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; using Microsoft.Practices.EnterpriseLibrary.Caching; public partial class Test : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { ICacheManager cacheManager = CacheFactory.GetCacheManager(); cacheManager.Add("s", TextBox1.Text, CacheItemPriority.Normal, null, new CacheItemDependency("s1")); this.Label1.Text = cacheManager.GetData("s") as string; } } protected void Button1_Click(object sender, EventArgs e) { ICacheManager cacheManager = CacheFactory.GetCacheManager(); DataAccessUtil.UpdateCacheDependency(new string[] { "s1" }); if (cacheManager.GetData("s") == null) { cacheManager.Add("s", TextBox1.Text, CacheItemPriority.Normal, null, new CacheItemDependency("s1")); } this.Label1.Text = cacheManager.GetData("s") as string; } }