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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
HttpContext.Current.Cache 和HttpRuntime.Cache的区别
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原文地址:http://www.cnblogs.com/slu182/p/4635217.html