Is it possible to iterate all the OutputCache keys? - asp.net

Question

Is it possible to iterate the OutputCache keys? I know you can remove them individually via HttpResponse.RemoveOutputCacheItem(), but is there a way I can iterate all the keys to see what's in the collection?
I searched through Object Viewer, but didn't see anything.
Worst case, I can maintain my own index. Since I'm doing everything by VaryByCustom, they get "fed" through a method in global.asax. It just strikes me that there has to be a more elegant way of doing this.

Answer 1

If you're using ASP.NET 4.0 you could do this by writing your own OutputCacheProvider. That would give you the ability to store the keys at the point that the item is cached:
namespace StackOverflowOutputCacheProvider
{
public class SOOutputCacheProvider: OutputCacheProvider
{
public override object Add(string key, object entry, DateTime utcExpiry)
{
// Do something here to store the key
// Persist the entry object in a persistence layer somewhere e.g. in-memory cache, database, file system
return entry;
}
...
}
}
You'd then be able to read the keys out from wherever you've stored them.

Answer 2

This can be accomplished by inheriting MemoryCache and exposing the enumerator via a custom OutputCacheProvider implementation. Keep in mind that the enumerator locks the cache. Enumerating over the cache should be executed infrequently.
namespace Caching
{
internal class MemoryCacheInternal : System.Runtime.Caching.MemoryCache
{
public MemoryCacheInternal(string name, System.Collections.Specialized.NameValueCollection config = null) : base(name, config)
{
}
public System.Collections.Generic.IEnumerator<System.Collections.Generic.KeyValuePair<string, object>> Enumerator()
{
return base.GetEnumerator();
}
}
}
Implement a custom OutputCacheProvider
using System.Web.Caching;
using System.Collections.Generic;
namespace Caching
{
public class EnumerableMemoryOutputCacheProvider : OutputCacheProvider, IEnumerable<KeyValuePair<string, object>>, IDisposable
{
private static readonly MemoryCacheInternal _cache = new MemoryCacheInternal("EnumerableMemoryOutputCache");
public override object Add(string key, object entry, System.DateTime utcExpiry)
{
return _cache.AddOrGetExisting(key, entry, UtcDateTimeOffset(utcExpiry));
}
public override object Get(string key)
{
return _cache.Get(key);
}
public override void Remove(string key)
{
_cache.Remove(key);
}
public override void Set(string key, object entry, System.DateTime utcExpiry)
{
_cache.Set(key, entry, UtcDateTimeOffset(utcExpiry));
}
public IEnumerator<KeyValuePair<string,object>> GetEnumerator()
{
return _cache.Enumerator();
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
return _cache.Enumerator();
}
private DateTimeOffset UtcDateTimeOffset(System.DateTime utcExpiry)
{
DateTimeOffset dtOffset = default(DateTimeOffset);
if ((utcExpiry.Kind == DateTimeKind.Unspecified)) {
dtOffset = DateTime.SpecifyKind(utcExpiry, DateTimeKind.Utc);
} else {
dtOffset = utcExpiry;
}
return dtOffset;
}
#region "IDisposable Support"
// To detect redundant calls
private bool disposedValue;
// IDisposable
protected virtual void Dispose(bool disposing)
{
if (!this.disposedValue) {
if (disposing) {
_cache.Dispose();
}
}
this.disposedValue = true;
}
public void Dispose()
{
// Do not change this code. Put cleanup code in Dispose(ByVal disposing As Boolean) above.
Dispose(true);
GC.SuppressFinalize(this);
}
#endregion
}
}
Configure the custom OutputCacheProvider
<system.web>
<caching>
<outputCache defaultProvider="EnumerableMemoryCache">
<providers>
<add name="EnumerableMemoryCache"
type="Caching.EnumerableMemoryOutputCacheProvider, MyAssemblyName"/>
</providers>
</outputCache>
<outputCacheSettings>
<outputCacheProfiles>
<add name="ContentAllParameters" enabled="false" duration="14400" location="Any" varyByParam="*"/>
</outputCacheProfiles>
</outputCacheSettings>
</caching>
</system.web>
Enumerate over the cache, in this case removing cache items.
OutputCacheProvider provider = OutputCache.Providers[OutputCache.DefaultProviderName];
if (provider == null) return;
IEnumerable<KeyValuePair<string, object>> keyValuePairs = provider as IEnumerable<KeyValuePair<string, object>>;
if (keyValuePairs == null) return;
foreach (var keyValuePair in keyValuePairs)
{
provider.Remove(keyValuePair.Key);
}

Answer 3

I have use this
http://www.codeproject.com/KB/session/exploresessionandcache.aspx
to view the cache and the session data. I only have to say that show only one pools data. If you have more pools, then you just see the one you are on it.