/// <summary>Getter for index</summary>
/// <param name="key">key to find (or load if needed)</param>
/// <param name="createItem">
/// An optional factory method for creating the item if it does not exist in the cache.
/// </param>
/// <returns>the object value associated with key, or null if not found or could not be loaded</returns>
public async Task <T> GetItem(TKey key, ItemCreator <TKey, T> createItem = null)
{
INode <T> node = FindExistingNodeByKey(key);
node?.Touch();
ItemCreator <TKey, T> creator = createItem ?? loadItem;
if ((node?.Value == null) && (creator != null))
{
Task <T> task = creator(key);
if (task == null)
{
throw new ArgumentNullException(nameof(createItem),
"Expected a non-null Task. Did you intend to return a null-returning Task instead?");
}
T value = await task;
lock (this)
{
node = FindExistingNodeByKey(key);
if (node?.Value == null)
{
node = owner.AddAsNode(value);
}
lifespanManager.CheckValidity();
}
}
return(node?.Value);
}
/// <summary>Getter for index</summary>
/// <param name="key">key to find (or load if needed)</param>
/// <param name="createItem">
/// An optional factory method for creating the item if it does not exist in the cache.
/// </param>
/// <returns>the object value associated with key, or null if not found or could not be loaded</returns>
public async Task <T> GetItem(TKey key, ItemCreator <TKey, T> createItem = null)
{
INode <T> node = FindExistingNodeByKey(key);
node?.Touch();
ItemCreator <TKey, T> creator = createItem ?? loadItem;
if ((node?.Value == null) && (creator != null))
{
T value = await creator(key);
lock (this)
{
node = FindExistingNodeByKey(key);
if (node?.Value == null)
{
node = owner.AddAsNode(value);
}
lifespanManager.CheckValidity();
}
}
return(node?.Value);
}
/// <summary>Getter for index</summary>
/// <param name="key">key to find (or load if needed)</param>
/// <returns>the object value associated with key, or null if not found & could not be loaded</returns>
public async Task <T> GetItem(TKey key, ItemLoader <TKey, T> loadItem = null)
{
INode <T> node = FindExistingNodeByKey(key);
node?.Touch();
lifespanManager.CheckValidity();
ItemLoader <TKey, T> loader = loadItem ?? this.loadItem;
if ((node?.Value == null) && (loader != null))
{
node = owner.AddAsNode(await loader(key));
}
return(node?.Value);
}