public async Task CacheExpirationTimeTest()
{
const int cacheSeconds = 2;
var testObject = new TestObject()
{
Name = "My Test"
};
var weakReference = new TimedCacheWeakReference <TestObject>(testObject, TimeSpan.FromSeconds(cacheSeconds));
Assert.IsTrue(weakReference.StrongReferenceAvailable, "No strong reference available");
//Drop my strong refrence, and perform a GC
testObject = null;
GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced);
//We are well within our cache time, so we should still have a reference
Assert.IsTrue(weakReference.StrongReferenceAvailable, "Lost reference before cache timeout expired");
//Now wait past our cache second time, then do a GC and verify we've lost the reference
await Task.Delay(TimeSpan.FromSeconds(cacheSeconds + 1));
GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced);
Assert.IsFalse(weakReference.StrongReferenceAvailable, "Strong reference is still available after cache expiration");
}
private static void RegisterExpiration(TimedCacheWeakReference <T> classToRegister, T target)
{
lock (cacheExpirationLock)
{
//Force set the target while we are within this class, in case it was cleared out in our expiration handler while we were waiting for the lock
classToRegister.strongReference = target;
var existing = registeredCacheExpirationItems.FirstOrDefault(item => item.TimedCacheWeakReference == classToRegister);
if (target == null)
{
//Strong reference has already been claimed, so remove this item from the collection
registeredCacheExpirationItems.Remove(existing);
}
else
{
if (existing == null)
{
//Register a new item for expiration
registeredCacheExpirationItems.Add(new CacheExpirationRecord()
{
ExpirationTime = DateTime.Now.Add(classToRegister.CacheDuration),
TimedCacheWeakReference = classToRegister
});
}
else
{
//Extend expiration lease
existing.ExpirationTime = DateTime.Now.Add(classToRegister.CacheDuration);
}
//Initialize our timer if it isn't already running
if (cacheExpirationTimer == null)
{
cacheExpirationTimer = new Timer(OnCacheExpirationTimer_Elapsed, null, cacheTimerInterval, cacheTimerInterval);
}
}
}
}