/// <summary>
/// Removes the single key resolver.
/// When process of retrieving data for specific key is finished.
/// Assigned process resolver is removed from the dictionary.
/// NOTE: All registered requests should have access, already have a task.
/// </summary>
/// <param name="key">The key used to identify assigned resolver.</param>
/// <param name="skr">The single key resolver instance to be removed.</param>
/// <returns>Task with information when key is removed from dictionary.</returns>
private async Task RemoveSingleKeyResolverAsync(TKey key, SingleKeyResolver skr)
{
await _lock.WaitAsync();
if (_dictionary.ContainsKey(key) && Object.ReferenceEquals(skr, _dictionary[key]))
{
_dictionary.Remove(key);
}
_lock.Release();
}
/// <summary>
/// Method assigns process responsible of retrieving data for specified key.
/// When method is called multiple times with same key
/// only first dataSupplier function/task will be executed.
/// </summary>
/// <param name="key">The key, to identify external resource.</param>
/// <param name="dataSupplier">The data supplier. Function responsible for retrieving data from external systems.
/// Function can call cache, call external system, update cache.</param>
/// <returns></returns>
public async Task <TResult> TakeResourceAsync(
TKey key,
Func <TKey, Task <TResult> > dataSupplier)
{
SingleKeyResolver singleKeyResolver = null;
await _lock.WaitAsync();
if (_dictionary.ContainsKey(key))
{
singleKeyResolver = _dictionary[key];
}
else
{
_dictionary[key] = singleKeyResolver = new SingleKeyResolver(key, this);
}
_lock.Release();
return(await singleKeyResolver.GetResourceAsync(dataSupplier).ConfigureAwait(false));
}