HttpContext.Current.Cache 和HttpRuntime.Cache的区别

红太狼 2022-08-10 12:44 140阅读 0赞

原文：[http://blog.csdn.net/qwlovedzm/article/details/7024405][http_blog.csdn.net_qwlovedzm_article_details_7024405]

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

[http_blog.csdn.net_qwlovedzm_article_details_7024405]: http://blog.csdn.net/qwlovedzm/article/details/7024405