HttpContext.Current.Cache和HttpRuntime.Cache的区别，以及System.Runtime.Caching

先看MSDN上的解释：
      HttpContext.Current.Cache：为当前 HTTP 请求获取Cache对象。
      HttpRuntime.Cache：获取当前应用程序的Cache。 
      我们再用.NET Reflector工具看看HttpContext.Cache和HttpRuntime.Cache的实现：

HttpContext.Cache和HttpRuntime.Cache实现
    //System.Web.HttpContext.Cache属性实现
    public sealed class HttpContext
    {
        public Cache Cache
        {
            get
            {
                return HttpRuntime.Cache;
            }
        }
    }

    //System.Web.HttpRuntime.Cache属性实现
    public sealed class HttpRuntime
    {
        public static Cache Cache
        {
            get
            {
                if (AspInstallDirectoryInternal == null)
                {
                    throw new HttpException(SR.GetString("Aspnet_not_installed", new object[] { VersionInfo.SystemWebVersion }));
                }
                Cache cache = _theRuntime._cachePublic;
                if (cache == null)
                {
                    CacheInternal cacheInternal = CacheInternal;
                    CacheSection cacheSection = RuntimeConfig.GetAppConfig().Cache;
                    cacheInternal.ReadCacheInternalConfig(cacheSection);
                    _theRuntime._cachePublic = cacheInternal.CachePublic;
                    cache = _theRuntime._cachePublic;
                }
                return cache;
            }
        }
    }

       通过上面的代码我们可以看出：HttpContext.Current.Cache是调用HttpRuntime.Cache实现的，两者指向同一Cache对象。那么两者到底有没有区别的？既然两个指向的是同一Cache对象，两者的差别只能出现在HttpContext和HttpRuntime上了。我们再来看看MSDN中HttpContext和HttpRuntime的定义。
      HttpContext：封装有关个别HTTP请求的所有HTTP特定的信息，HttpContext.Current为当前的HTTP请求获取HttpContext对象。
      HttpRuntime：为当前应用程序提供一组ASP.NET运行时服务。

      由上面的定义可以看出：HttpRuntime.Cache相当于就是一个缓存具体实现类，这个类虽然被放在了System.Web命名空间下，但是非Web应用下也是可以使用；HttpContext.Current.Cache是对上述缓存类的封装，由于封装到了HttpContext类中，局限于只能在知道HttpContext下使用，即只能用于Web应用。

      下面的例子可以很好的说明这一点：

HttpContext.Cache和HttpRuntime.Cache的示例
    class CacheTest
    {
        static void Main(string[] args)
        {       
            System.Web.Caching.Cache httpRuntimeCache = System.Web.HttpRuntime.Cache;
            httpRuntimeCache.Insert("httpRuntimeCache", "I am stored in HttpRuntime.Cache");

            if (httpRuntimeCache != null)
            {
                Console.WriteLine("httpRuntimeCache:" + httpRuntimeCache["httpRuntimeCache"]);
            }

            System.Web.HttpContext httpContext = System.Web.HttpContext.Current;
            if (httpContext == null)
            {
                Console.WriteLine("HttpContext object is null in Console Project");
            }
            else
            {
                System.Web.Caching.Cache httpContextCache = httpContext.Cache;
                httpContextCache.Insert("httpContextCache", "I am stored in HttpRuntime.Cache");
                if (httpContextCache == null)
                {
                    Console.WriteLine("httpContextCache is null");
                }
            }
             
            Console.ReadLine();
        }
    }

      输出结果：httpRuntimeCache:I am stored in HttpRuntime.Cache
      HttpContext object is null in Console Project

      综上：我们在使用Cache时，尽量使用HttpRuntime.Cache，既能减少出错，也减少了一次函数调用。

      参考资料：HttpRuntime.Cache 与HttpContext.Current.Cache的疑问，HttpRuntime.Cache vs. HttpContext.Current.Cache

 

出处：http://blog.csdn.net/qwlovedzm/article/details/7024405

===============================================================================

下面我们看看简单的缓存类处理：

using System;
using System.Collections;
using System.Web;
using System.Web.Caching;namespace aaaaa.Api.Business
{/// <summary>/// 缓存类/// </summary>public class CacheHelper{/// <summary>/// 增加一个缓存对象/// </summary>/// <param name="strKey">键值名称</param>/// <param name="valueObj">被缓存对象</param>/// <param name="durationMin">缓存失效时间（默认为5分钟）</param>/// <param name="cachePriority">保留优先级(枚举数值)</param>/// <returns>缓存写入是否成功true 、false</returns>public static bool InsertCach(string strKey, object valueObj, int durationMin,CacheItemPriority cachePriority = CacheItemPriority.Default){TimeSpan ts;if (!string.IsNullOrWhiteSpace(strKey) && valueObj != null){//onRemove是委托执行的函数，具体方法看下面的onRemove(...)CacheItemRemovedCallback callBack = new CacheItemRemovedCallback(onRemove);ts = durationMin == 0 ? new TimeSpan(0, 5, 0) : new TimeSpan(0, durationMin, 0);//HttpContext.Current.Cache.Insert(
                HttpRuntime.Cache.Insert(strKey,valueObj,null,DateTime.Now.Add(ts),Cache.NoSlidingExpiration,cachePriority,callBack);return true;}else{return false;}}/// <summary>/// 判断缓存对象是否存在/// </summary>/// <param name="strKey">缓存键值名称</param>/// <returns>是否存在true 、false</returns>public static bool IsExist(string strKey){//return HttpContext.Current.Cache[strKey] != null;return HttpRuntime.Cache.Get(strKey) != null;}/// <summary>/// 读取缓存对象/// </summary>/// <param name="strKey">缓存键值名称</param>/// <returns>缓存对象，objec类型</returns>public static object GetCache(string strKey){//if (HttpContext.Current.Cache[strKey] != null)if (IsExist(strKey)){object obj = HttpRuntime.Cache.Get(strKey);return obj ?? null;}else{return null;}}/// <summary>/// 移除缓存对象/// </summary>/// <param name="strKey">缓存键值名称</param>public static void Remove(string strKey){//if (HttpContext.Current.Cache[strKey] != null)if (IsExist(strKey)){HttpRuntime.Cache.Remove(strKey);}}/// <summary>/// 清除所有缓存/// </summary>public static void Clear(){IDictionaryEnumerator enu = HttpRuntime.Cache.GetEnumerator();while (enu.MoveNext()){Remove(enu.Key.ToString());}}public static CacheItemRemovedReason reason;/// <summary>/// 此方法在值失效之前调用，可以用于在失效之前更新数据库，或从数据库重新获取数据/// </summary>/// <param name="strKey"></param>/// <param name="obj"></param>/// <param name="reason"></param>private static void onRemove(string strKey, object obj, CacheItemRemovedReason r){reason = r;}//...
}
}

 

出处：http://blog.csdn.net/joyhen/article/details/40379145

=======================================================================

引用：System.Runtime.Caching.dll，如下测试，fm4.5

static void CacheTest(){string cname = "filescontents";ObjectCache cc = MemoryCache.Default;string fileContents = cc[cname] as string;if (fileContents == null){CacheItemPolicy policy = new CacheItemPolicy();TimeSpan sp = new TimeSpan(0, 1, 0);policy.SlidingExpiration = sp;List<string> filePaths = new List<string>();string path = System.IO.Directory.GetCurrentDirectory() + "\\example.txt";filePaths.Add(path);policy.ChangeMonitors.Add(new HostFileChangeMonitor(filePaths));fileContents = System.IO.File.ReadAllText(path, Encoding.Default);cc.Set(cname, fileContents, policy);}Console.WriteLine(fileContents);}static void Main(string[] args){//ExecuteCode(WriteData);//ExecuteCode(ReadData);//ExecuteCode(TransData);bool quit = false;while (!quit){Console.Write("get cache: ");string demo = Console.ReadLine();switch (demo){case "Y": ExecuteCode(CacheTest); break;case "Q":quit = true;break;default:Console.WriteLine("Choose a Word of Y and Q(to quit)");break;}}Console.ReadKey();}public static void ExecuteCode(Action a){System.Diagnostics.Stopwatch stopwatch = new System.Diagnostics.Stopwatch();stopwatch.Start();a();stopwatch.Stop();TimeSpan timespan = stopwatch.Elapsed;Console.WriteLine("运行{0}秒", timespan.TotalSeconds);}

 

出处：http://blog.csdn.net/joyhen/article/details/39990455