using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Caching;
using System.Text;
using System.Threading.Tasks;
namespace GetCachable
{publicstaticclass BetterCacheManager
{//加入Lock機制限定同一Key同一時間只有一個Callback執行
conststring AsyncLockPrefix = "$$CacheAsyncLock#";
/// <summary>
/// 取得每個Key專屬的鎖定對象
/// </summary>
/// <param name="key">Cache保存號碼牌</param>
/// <returns></returns>
staticobject GetAsyncLock(string key)
{ ObjectCache cache = MemoryCache.Default;
//取得每個Key專屬的鎖定對象（object）
string asyncLockKey = AsyncLockPrefix + key;
lock (cache)
{if (cache[asyncLockKey] == null) cache.Add(asyncLockKey,
newobject(),
new CacheItemPolicy() { SlidingExpiration = new TimeSpan(0, 10, 0)
});
}
return cache[asyncLockKey];
}
/// <summary>
/// 取得可以被Cache的資料(注意：非Thread-Safe)
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="key">Cache保存號碼牌</param>
/// <param name="callback">傳回查詢資料的函數</param>
/// <param name="cacheMins"></param>
/// <param name="forceRefresh">是否清除Cache，重新查詢</param>
/// <returns></returns>
publicstatic T GetCachableData<T>(string key, Func<T> callback,
int cacheMins, bool forceRefresh = false) where T : class
{ ObjectCache cache = MemoryCache.Default;
string cacheKey = key;
//取得每個Key專屬的鎖定對象
lock (GetAsyncLock(key))
{ T res = cache[cacheKey] as T;
//是否清除Cache，強制重查
if (res != null&& forceRefresh)
{ cache.Remove(cacheKey);
res = null;
}
if (res == null)
{ res = callback();
cache.Add(cacheKey, res,
new CacheItemPolicy() { SlidingExpiration = new TimeSpan(0, cacheMins, 0)
});
}
return res;
}
}
/// <summary>
/// 取得可以被Cache的資料(注意：非Thread-Safe)
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="key">Cache保存號碼牌</param>
/// <param name="callback">傳回查詢資料的函數</param>
/// <param name="absExpire">有效期限</param>
/// <param name="forceRefresh">是否清除Cache，重新查詢</param>
/// <returns></returns>
publicstatic T GetCachableData<T>(string key, Func<T> callback,
DateTimeOffset absExpire, bool forceRefresh = false) where T : class
{ ObjectCache cache = MemoryCache.Default;
string cacheKey = key;
//取得每個Key專屬的鎖定對象
lock (GetAsyncLock(key))
{ T res = cache[cacheKey] as T;
//是否清除Cache，強制重查
if (res != null&& forceRefresh)
{ cache.Remove(cacheKey);
res = null;
}
if (res == null)
{ res = callback();
cache.Add(cacheKey, res, new CacheItemPolicy()
{ AbsoluteExpiration = absExpire
});
}
return res;
}
}
}
}
