Generic wrapper for System.Web.Caching.Cache functions

Question

I've created a generic wrapper for using the Cache object:

public class Cache<T> where T : class
{
    public Cache Cache {get;set;}
    public CachedKeys Key {get;set;}

    public Cache(Cache cache, CachedKeys key){
        Cache = cache;
        Key = key;
    }

    public void AddToCache(T obj){
        Cache.Add(Key.ToString(),
            obj,
            null,
            DateTime.Now.AddMinutes(5),
            System.Web.Caching.Cache.NoSlidingExpiration,
            System.Web.Caching.CacheItemPriority.Normal,
            null);                   
    }

    public bool TryGetFromCache(out T cachedData) {
        cachedData = Cache[Key.ToString()] as T;
        return cachedData != null;
    }

    public void RemoveFromCache() {
        Cache.Remove(Key.ToString()); }
}

The CachedKeys enumeration is just a list of keys that can be used to cache data.

The trouble is, to call it is quite convuluted:

var cache = new Cache<MyObject>(Page.Cache, CachedKeys.MyKey);
MyObject myObject = null;

if(!cache.TryGetFromCache(out myObject)){
    //get data...
    cache.AddToCache(data); //add to cache
    return data;
}

return myObject;

I only store one instance of each of my objects in the cache.

Therefore, is there any way that I can create an extension method that accepts the type of object to Cache and uses (via Reflection) its Name as the cache key?

public static Cache<T> GetCache(this Cache cache, Type cacheType){
        Cache<cacheType> Cache = new Cache<cacheType>(cache, cacheType.Name);
    }

Of course, there's two errors here:

• Extension methods must be defined in a non-generic static class
• The type or namespace name 'cacheType' could not be found

This is clearly not the right approach but I thought I'd show my working. Could somebody guide me in the right direction?

Answer 1

How about:

public static Cache<T> GetCache<T>(this Cache cache)
{
    return new Cache<T>(cache, typeof(T).Name);
}

This will of course have to be defined in another class.

Answer 2

I ended up using generic extension methods:

public static class CacheExtensions
{
    public static void Remove<T>(this Cache cache) where T : class
    {
        cache.Remove(typeof(T).Name);
    }

    public static void AddToCache<T>(this Cache cache, object item) where T : class
    {
        T outItem = null;
        if (cache.TryGetItemFromCache<T>(out outItem))
            throw new ArgumentException("This item is already in the cache");

        cache.Insert(typeof(T).Name,
                item,
                null,
                DateTime.Now.AddMinutes(5),
                System.Web.Caching.Cache.NoSlidingExpiration,
                System.Web.Caching.CacheItemPriority.Normal,
                null);
    }

    public static bool TryGetItemFromCache<T>(this Cache cache, out T item) where T : class
    {
         item = cache.Get(typeof(T).Name) as T;
         return item != null;
    }
}

Called like:

MyObject myObject = null;
if(!Cache.TryGetItemFromCache(out myObject)){
     //get data
     Cache.AddToCache<MyObject>(data);
}

and..

Cache.Remove<MyObject>();

Answer 3

I think the following method needs to be changed:

 public static bool TryGetItemFromCache<T>(this Cache cache, out T item) where T : class
    {
         item = cache.Get(typeof(T).Name) as T;
         return item != null;
    }

If the item is not in the cache don't you want to put the item in the cache for later use or later retrieval.

Thanks,