Programmatically clearing cache from OutputCacheAttribute? - asp.net-mvc-3

Question

In our code we have an MVC controller action that is decorated with the OutputCacheAttribute. Is there any way in some other action to clear the cache for the first action?

Answer 1

It depends. If it is a child action the cache is stored in the MemoryCache and the only way to clear it is undocumented and involves busting the whole memory cache:
OutputCacheAttribute.ChildActionCache = new MemoryCache("NewDefault");
The drawback of course is that this removes all cached child actions and not just the cached output of this child action. If it is a normal action then you could use the Response.RemoveOutputCacheItem method by passing it the url of the action that was cached. You might also find the following article interesting.
Caching in ASP.NET MVC 3 has still a very long way to go. Hopefully they are improving many things in ASP.NET MVC 4 and simplifying it.

Answer 2

Yes, it is possible
I have found the answer in this book.
See 14.3 Output Cache In ASP.NET MVC
page 372 - Deterministically removing items from cache
When we decorate an action with the OutputCacheAttribute , OutputCache
stores its result into ASP.NET Cache and automatically recovers it
when it must serve a subse- quent analogous request. If we knew which
cache key the page belongs to, we could easily remove it.
Unfortunately, this isn’t easily possible, and even if it were, we
aren’t supposed to know it because it resides in the internal logic
of the caching infrastruc- ture and might change without notice in
future releases. What we can do, though, is leverage the cache
dependencies mechanism to achieve a similar result. This feature is
similar to the change monitors we’re going to talk about in section
14.4. Leveraging cache dependencies consists of tying one cache entry to another to automatically remove the first one when the latter is invalidated.
And a piece of code
public class DependencyOutputCacheAttribute : OutputCacheAttribute
{
public string ParameterName { get; set; }
public string BasePrefix { get; set; }
public override void OnResultExecuting(ResultExecutingContext filterContext)
{
base.OnResultExecuting( filterContext );
string key = string.IsNullOrEmpty( BasePrefix )
? filterContext.RouteData.Values["action"] + "_" + filterContext.RouteData.Values["controller"]
: BasePrefix;
key = AddToCache( filterContext, key, ParameterName);
}
private string AddToCache(ResultExecutingContext filterContext, string key, string parameter)
{
if ( !string.IsNullOrEmpty( parameter ) && filterContext.RouteData.Values[parameter] != null) {
key += "/" + filterContext.RouteData.Values[parameter];
filterContext.HttpContext.Cache.AddBig( key, key );
filterContext.HttpContext.Response.AddCacheItemDependency( key );
}
return key;
}
}
And Remove cache dependency attribute
public class RemoveCachedAttribute : ActionFilterAttribute
{
public string ParameterName { get; set; }
public string BasePrefix { get; set; }
public override void OnResultExecuting( ResultExecutingContext filterContext)
{
base.OnResultExecuting(filterContext);
string key = string.IsNullOrEmpty(BasePrefix) ?
filterContext.RouteData.Values["action"].ToString() + "_" +
filterContext.RouteData.Values["controller"].ToString() : BasePrefix;
if (!string.IsNullOrEmpty(ParameterName))
key += filterContext.RouteData.Values[ParameterName];
filterContext.HttpContext.Cache.Remove(key);
}
}
and finally use it
[DependencyCache( BasePrefix = "Story", ParameterName = "id" )]
public virtual ActionResult ViewStory(int id){
//load story here
}
[HttpPost, RemoveCache( BasePrefix = "Story", ParameterName = "id" )]
public virtual ActionResult DeleteStory(int id){
//submit updated story version
}
[HttpPost, RemoveCache( BasePrefix = "Story", ParameterName = "id" )]
public virtual ActionResult EditStory(Story txt){
//submit updated story version
}
where
public class Story {
int id {get;set;} //case is important
string storyContent{get;set;}
}