System.Runtime.Cache expires instantly
I have a web page that caches some request values for 30 seconds to avoid getting duplicate values. I am using the following class:
public class MyCache {
private static ObjectCache cache = MemoryCache.Default;
public MyCache() { }
public void Insert(string key, string value)
{
CacheItemPolicy policy = new CacheItemPolicy();
policy.Priority = CacheItemPriority.Default;
policy.SlidingExpiration = new TimeSpan(0, 0, 30);
policy.RemovedCallback = new CacheEntryRemovedCallback(this.Cacheremovedcallback);
cache.Set(key, value, policy);
}
public bool Exists(string key)
{
return cache.Contains(key);
}
public void Remove(string key)
{
cache.Remove(key);
}
private void Cacheremovedcallback(CacheEntryRemovedArguments arguments)
{
FileLog.LogToFile("Cache item removed. Reason: " + arguments.RemovedReason.ToString() + "; Item: [" + arguments.CacheItem.Key + ", " + arguments.CacheItem.Value.ToString() + "]");
}
}
This works great for a few weeks and then the cache no longer stores the values. The CacheRemoved callback is triggered instantly after the item is inserted into the cache and I get the remote reason: CacheSpecificEviction This is running on Windows Server 2008 SP1, IIS7.5 with .NET 4.0. During this time, no changes were applied to the OS or IIS.
Is there a way to solve this, and if not, is there a better cache solution to use in a web page?
Thanks in advance.
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1 answer
Try the following:
policy.AbsoluteExpiration = DateTime.Now.AddSeconds(30);
This is how I use Cache:
public static class CacheHelper
{
private static ObjectCache _cache;
private const Double ChacheExpirationInMinutes = 10;
/// <summary>
/// Insert value into the cache using
/// appropriate name/value pairs
/// </summary>
/// <typeparam name="T">Type of cached item</typeparam>
/// <param name="entity">item cached</param>
/// <param name="key">Name of item</param>
public static void Add<T>(T entity, string key) where T : class
{
if (_cache == null)
{
_cache = MemoryCache.Default;
}
if (_cache.Contains(key))
_cache.Remove(key);
CacheItemPolicy cacheItemPolicy = new CacheItemPolicy();
cacheItemPolicy.AbsoluteExpiration = DateTime.Now.AddMinutes(ChacheExpirationInMinutes);
_cache.Set(key, entity, cacheItemPolicy);
}
/// <summary>
/// Remove item from cache
/// </summary>
/// <param name="key">Name of cached item</param>
public static void Clear(string key)
{
if (_cache == null)
{
_cache = MemoryCache.Default;
return;
}
_cache.Remove(key);
}
/// <summary>
/// Retrieve cached item
/// </summary>
/// <typeparam name="T">Type of cached item</typeparam>
/// <param name="key">Name of cached item</param>
/// <returns>Cached item as type</returns>
public static T Get<T>(string key) where T : class
{
if (_cache == null)
{
_cache = MemoryCache.Default;
}
try
{
return (T)_cache.Get(key);
}
catch
{
return null;
}
}
}
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