我在我的Application_Start中有这个：
var crumbsCache = new MemoryCache("breadCrumbsNames");
var crumbsList = new List<CacheItem>
{
//list of new CacheItem();
};
foreach (var cacheItem in crumbsList)
{
crumbsCache.Add(cacheItem,new CacheItemPolicy());
}
现在,在我的控制器中,我这样做：
var cache = new MemoryCache("breadCrumbsNames");
var cacheItem = cache.GetCacheItem("nameOfCacheItem");
但是然后cacheItem总是为null,我做错了什么？
解决方法
我认为更好的选择是使用Ninject或其他依赖注入框架,根据需要将MemoryCache注入控制器.
首先,将Ninject和Ninject.Mvc3(以及任何其他相关位)添加到ASP.NET MVC项目中.如果您在Visual Studio中工作,则可以使用NuGet来执行此操作.它非常轻松,自动化程度很高.
下一步是将MemoryCache包装成某种接口,例如：
public interface IMemoryCacheService
{
MemoryCache MemoryCache
{
get;
set;
}
}
和：
public class MemoryCacheService : IMemoryCacheService
{
public MemoryCacheService()
{
MemoryCache = new MemoryCache();
}
public MemoryCache MemoryCache
{
get;
set;
}
}
然后在Ninject中定义一个绑定,以便Ninject知道当你需要某种类型的IMemoryCacheService时,它应该为你提供MemoryCacheService的实例.
我将在这里粘贴我自己的Ninject配置类.将在您的项目中创建的那个将非常相似,并将位于名为App_Start的文件夹中(如果您使用NuGet将自动创建). Ninject默认创建的类称为NinjectWebCommon.
public static class NinjectConfig
{
private static readonly Bootstrapper bootstrapper = new Bootstrapper();
public static void Start()
{
DynamicModuleUtility.RegisterModule(typeof(OnePerRequestHttpModule));
DynamicModuleUtility.RegisterModule(typeof(NinjectHttpModule));
bootstrapper.Initialize(CreateKernel);
}
public static void Stop()
{
bootstrapper.ShutDown();
}
private static IKernel CreateKernel()
{
var kernel = new StandardKernel();
kernel.Bind<Func<IKernel>>()
.ToMethod(context => () => new Bootstrapper().Kernel);
kernel.Bind<IHttpModule>()
.To<HttpApplicationInitializationHttpModule>();
kernel.RegisterServices();
return kernel;
}
private static void RegisterServices(this IKernel kernel)
{
kernel.Bind<IMemoryCacheService>()
.To<MemoryCacheService>()
.InSingletonScope();
// InSingletonScope() is important so Ninject knows
// to create only one copy and then reuse it every time
// it is asked for
// ignore the stuff below... I have left it in here for illustration
kernel.Bind<IDbTransactionFactory>()
.To<DbTransactionFactory>()
.InRequestScope();
kernel.Bind<IDbModelContext>()
.To<DbModelContext>()
.InRequestScope();
kernel.Bind<IDbModelChangeContext>()
.To<DbModelChangeContext>()
.InRequestScope();
kernel.Bind<IUserContext>()
.To<UserContext>()
.InRequestScope();
kernel.BindAttributeAndFilter<IgnoreNonAjaxRequestsFilter,IgnoreNonAjaxRequestsAttribute>();
kernel.BindAttributeAndFilter<ProvideApplicationInfoFilter,ProvideApplicationInfoAttribute>();
kernel.BindAttributeAndFilter<ProvideSessionInfoFilter,ProvideSessionInfoAttribute>();
kernel.BindAttributeAndFilter<UseDialogLayoutFilter,UseDialogLayoutAttribute>();
kernel.BindAttributeAndFilter<CheckResourceAccessFilter,CheckResourceAccessAttribute>();
kernel.BindAttributeAndFilter<CheckResourceStateFilter,CheckResourceStateAttribute>();
}
private static void BindAttributeAndFilter<TFilter,TAttribute>(this IKernel kernel)
{
kernel.BindFilter<TFilter>(FilterScope.Action,null)
.WhenControllerHas<TAttribute>();
kernel.BindFilter<TFilter>(FilterScope.Action,null)
.WhenActionMethodHas<TAttribute>();
}
}
最后,您的控制器将从以下更改：
public class HomeController : Controller
{
public ActionResult Foo()
{
...
}
...
}
至：
public class HomeController : Controller
{
private IMemoryCacheService memoryCacheService;
public HomeController(IMemoryCacheService memoryCacheService)
{
this.memoryCacheService = memoryCacheService;
}
public ActionResult Foo()
{
// use this.memoryCacheService in your controller methods...
}
...
}
比方说,您按照上述策略制作了另一个名为IEmailService的服务,并且您希望IEmailService也可以在HomeController中使用,然后：
public class HomeController : Controller
{
private IMemoryCacheService memoryCacheService;
private IEmailService emailService;
public HomeController(IMemoryCacheService memoryCacheService,IEmailService emailService)
{
this.memoryCacheService = memoryCacheService;
this.emailService = emailService;
}
public ActionResult Foo()
{
// use this.memoryCacheService in your controller methods...
// and also use this.emailService in your controller methods...
}
...
}
