艾伟_转载：企业库缓存依赖的实现基于文件依赖狼人:

最近在做项目的时候，采用用Codesmith和Nettiers生成的框架来实现，生成的代码核心是基于企业库的。所以最近在恶补企业库，对于缓存的学习当然是必不可少的，尤其是经常要用到得缓存依赖，这里我用到的是文件依赖来举例子，其他的都大同小异，主要就是要实现ICacheItemExpiration中的返回值类型为bool类型的HasExpired方法，来控制到期与否，实现此方法是关键所在。下面是程序清单，欢迎大家指正：

step1 实现缓存到期接口，此类就为缓存项依赖的类，为缓存依赖的核心，尤其是其中HasExpired方法的定义，此类的核心就是使用lastCount是否变化来判断缓存是否到期；如果有变化则HasExpired方法返回true,否则返回false。

Code
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

Code
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 测试实体，下面只是个简单的测试，大家可以发散一下，写出更加有复用性的方法。

Code
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;
    }
}

艾伟_转载：企业库缓存依赖的实现基于文件依赖 狼人:

艾伟_转载：企业库缓存依赖的实现基于文件依赖狼人: