/// <summary>
/// Initializes a new instance of the <see cref="ReferenceCountingCacheItemProxy" /> class.
/// </summary>
/// <param name="cacheItem">
/// The cache item that this proxy will used to access the underlying object represented.
/// </param>
/// <exception cref="ArgumentNullException">
/// <paramref name="cacheItem" /> is <see langword="null" />.
/// </exception>
// Disabled warning about non-null member (_cacheItem) being set as it will always be set before use.
// ReSharper disable once NotNullMemberIsNotInitialized
protected ReferenceCountingCacheItemProxy(
[JetBrains.Annotations.NotNull] ReferenceCountingCacheItem <TKey, TItem, TProxy> cacheItem)
{
cacheItem.Validate(nameof(cacheItem), ObjectIs.NotNull);
_cacheItem = cacheItem;
_cacheItem.AddReference();
_token = _cacheItem.Token;
}
public TProxy this[[JetBrains.Annotations.NotNull] TKey key]
{
get
{
CheckNotDisposed();
key.Validate(nameof(key), ObjectIs.NotNull);
// Our first attempt is from outside any locking
ReferenceCountingCacheItem <TKey, TItem, TProxy> cachedItem;
if (!_cache.TryGetValue(key, out cachedItem))
{
// No luck? Then get exclusive access and try again.
_lock.EnterWriteLock();
try
{
// Someone else was in the process of creating it when we entered the lock.
if (!_cache.TryGetValue(key, out cachedItem))
{
// Still no luck, then we will need to create a cache entry
cachedItem = new ReferenceCountingCacheItem <TKey, TItem, TProxy>(_createItem, key);
_cache.Add(key, cachedItem);
cachedItem.CacheItemDisposed += CachedItemDisposed;
}
}
finally
{
_lock.ExitWriteLock();
}
}
Debug.Assert(cachedItem != null, "cachedItem != null");
// Call the GetItem method from outside any locking - it will perform its own locking internally until
// the item has been created.
var proxy = _proxyFactory(cachedItem);
if (proxy == null)
{
throw new InvalidOperationException(string.Format(CultureInfo.InvariantCulture,
Resources.Exceptions.DelegateReturnedNull, "_proxyFactory"));
}
proxy.ProxyFactory = _proxyFactory;
return(proxy);
}
}
