/// <summary>
/// Attempt to insert item into cache.
/// </summary>
/// <param name="key">Key of the item to be inserted in the cache.</param>
/// <param name="value">Value of the item to be inserted in the cache.</param>
/// <returns><c>true</c> when the key does not already exist in the cache, <c>false</c> otherwise.</returns>
public bool TryAddValue(TKey key, TValue value)
{
lock (_dictionary)
{
MruCacheItem item;
if (_dictionary.TryGetValue(key, out item))
{
var version = _currentVersion;
if (item.Version != version || !EqualityComparer <TValue> .Default.Equals(value, item.Value))
{
_dictionary[key] = new MruCacheItem(value, version, false);
}
return(false); // Already exists
}
else
{
if (_dictionary.Count >= _maxCapacity)
{
++_currentVersion;
PruneCache();
}
_dictionary.Add(key, new MruCacheItem(value, _currentVersion, true));
return(true);
}
}
}
/// <summary>
/// Lookup existing item in cache.
/// </summary>
/// <param name="key">Key of the item to be searched in the cache.</param>
/// <param name="value">Output value of the item found in the cache.</param>
/// <returns><c>True</c> when the key is found in the cache, <c>false</c> otherwise.</returns>
public bool TryGetValue(TKey key, out TValue value)
{
MruCacheItem item;
try
{
if (!_dictionary.TryGetValue(key, out item))
{
value = default(TValue);
return(false);
}
}
catch
{
item = default(MruCacheItem); // Too many people in the same room
}
if (item.Version != _currentVersion || item.Virgin)
{
// Update item version to mark as recently used
lock (_dictionary)
{
var version = _currentVersion;
if (_dictionary.TryGetValue(key, out item))
{
if (item.Version != version || item.Virgin)
{
if (item.Virgin)
{
version = ++_currentVersion;
}
_dictionary[key] = new MruCacheItem(item.Value, version, false);
}
}
else
{
value = default(TValue);
return(false);
}
}
}
value = item.Value;
return(true);
}
