.NET中Cache有两种调用方式：HttpContext.Current.Cache 和 HttpRuntime.Cache，这两种方式有什么区别呢？我们先看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.Current.Cache 和 HttpRuntime.Cache 
HttpContext.Current.Cache 和 HttpRuntime.Cache //System.Web.HttpContext.Cache属性实现
HttpContext.Current.Cache 和 HttpRuntime.Cache public sealed class HttpContext
HttpContext.Current.Cache 和 HttpRuntime.Cache {
HttpContext.Current.Cache 和 HttpRuntime.Cache public Cache Cache
HttpContext.Current.Cache 和 HttpRuntime.Cache {
HttpContext.Current.Cache 和 HttpRuntime.Cache get
HttpContext.Current.Cache 和 HttpRuntime.Cache {
HttpContext.Current.Cache 和 HttpRuntime.Cache return HttpRuntime.Cache;
HttpContext.Current.Cache 和 HttpRuntime.Cache }
HttpContext.Current.Cache 和 HttpRuntime.Cache }
HttpContext.Current.Cache 和 HttpRuntime.Cache }
HttpContext.Current.Cache 和 HttpRuntime.Cache HttpContext.Current.Cache 和 HttpRuntime.Cache HttpContext.Current.Cache 和 HttpRuntime.Cache //System.Web.HttpRuntime.Cache属性实现
HttpContext.Current.Cache 和 HttpRuntime.Cache public sealed class HttpRuntime
HttpContext.Current.Cache 和 HttpRuntime.Cache {
HttpContext.Current.Cache 和 HttpRuntime.Cache public static Cache Cache
HttpContext.Current.Cache 和 HttpRuntime.Cache {
HttpContext.Current.Cache 和 HttpRuntime.Cache get
HttpContext.Current.Cache 和 HttpRuntime.Cache {
HttpContext.Current.Cache 和 HttpRuntime.Cache if (AspInstallDirectoryInternal == null)
HttpContext.Current.Cache 和 HttpRuntime.Cache {
HttpContext.Current.Cache 和 HttpRuntime.Cache throw new HttpException(SR.GetString("Aspnet_not_installed", new object[] { VersionInfo.SystemWebVersion }));
HttpContext.Current.Cache 和 HttpRuntime.Cache }
HttpContext.Current.Cache 和 HttpRuntime.Cache Cache cache = _theRuntime._cachePublic;
HttpContext.Current.Cache 和 HttpRuntime.Cache if (cache == null)
HttpContext.Current.Cache 和 HttpRuntime.Cache {
HttpContext.Current.Cache 和 HttpRuntime.Cache CacheInternal cacheInternal = CacheInternal;
HttpContext.Current.Cache 和 HttpRuntime.Cache CacheSection cacheSection = RuntimeConfig.GetAppConfig().Cache;
HttpContext.Current.Cache 和 HttpRuntime.Cache cacheInternal.ReadCacheInternalConfig(cacheSection);
HttpContext.Current.Cache 和 HttpRuntime.Cache _theRuntime._cachePublic = cacheInternal.CachePublic;
HttpContext.Current.Cache 和 HttpRuntime.Cache cache = _theRuntime._cachePublic;
HttpContext.Current.Cache 和 HttpRuntime.Cache }
HttpContext.Current.Cache 和 HttpRuntime.Cache return cache;
HttpContext.Current.Cache 和 HttpRuntime.Cache }
HttpContext.Current.Cache 和 HttpRuntime.Cache }
HttpContext.Current.Cache 和 HttpRuntime.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.Current.Cache 和 HttpRuntime.Cache HttpContext.Current.Cache 和 HttpRuntime.Cache class CacheTest
HttpContext.Current.Cache 和 HttpRuntime.Cache {
HttpContext.Current.Cache 和 HttpRuntime.Cache static void Main(string[] args)
HttpContext.Current.Cache 和 HttpRuntime.Cache {
HttpContext.Current.Cache 和 HttpRuntime.Cache System.Web.Caching.Cache httpRuntimeCache = System.Web.HttpRuntime.Cache;
HttpContext.Current.Cache 和 HttpRuntime.Cache httpRuntimeCache.Insert("httpRuntimeCache", "I am stored in HttpRuntime.Cache");
HttpContext.Current.Cache 和 HttpRuntime.Cache HttpContext.Current.Cache 和 HttpRuntime.Cache if (httpRuntimeCache != null)
HttpContext.Current.Cache 和 HttpRuntime.Cache {
HttpContext.Current.Cache 和 HttpRuntime.Cache Console.WriteLine("httpRuntimeCache:" + httpRuntimeCache["httpRuntimeCache"]);
HttpContext.Current.Cache 和 HttpRuntime.Cache }
HttpContext.Current.Cache 和 HttpRuntime.Cache HttpContext.Current.Cache 和 HttpRuntime.Cache System.Web.HttpContext httpContext = System.Web.HttpContext.Current;
HttpContext.Current.Cache 和 HttpRuntime.Cache if (httpContext == null)
HttpContext.Current.Cache 和 HttpRuntime.Cache {
HttpContext.Current.Cache 和 HttpRuntime.Cache Console.WriteLine("HttpContext object is null in Console Project");
HttpContext.Current.Cache 和 HttpRuntime.Cache }
HttpContext.Current.Cache 和 HttpRuntime.Cache else
HttpContext.Current.Cache 和 HttpRuntime.Cache {
HttpContext.Current.Cache 和 HttpRuntime.Cache System.Web.Caching.Cache httpContextCache = httpContext.Cache;
HttpContext.Current.Cache 和 HttpRuntime.Cache httpContextCache.Insert("httpContextCache", "I am stored in HttpRuntime.Cache");
HttpContext.Current.Cache 和 HttpRuntime.Cache if (httpContextCache == null)
HttpContext.Current.Cache 和 HttpRuntime.Cache {
HttpContext.Current.Cache 和 HttpRuntime.Cache Console.WriteLine("httpContextCache is null");
HttpContext.Current.Cache 和 HttpRuntime.Cache }
HttpContext.Current.Cache 和 HttpRuntime.Cache }
HttpContext.Current.Cache 和 HttpRuntime.Cache HttpContext.Current.Cache 和 HttpRuntime.Cache Console.ReadLine();
HttpContext.Current.Cache 和 HttpRuntime.Cache }
HttpContext.Current.Cache 和 HttpRuntime.Cache }
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
