public async Task Refresh(string key, Func <Task <IDocument> > doc, Func <Task <Stream> > stream)
{
if (!AllocatedFiles.Contains(key))
{
AllocatedFiles.Add(key);
await CacheInvalidator.Allocated(key, doc, stream);
}
else
{
await CacheInvalidator.Refresh(key, doc, stream);
}
}