private List <T> GetCachedItems <TU>(IEnumerable <TU> keys)
{
var results = new List <T>();
foreach (var key in keys)
{
if (primaryCache.Contains(key))
{
results.Add(CacheLock.Read(Lock, () => primaryCache.GetByKey(key)));
}
else
{
results.AddRange(CacheLock.Read(Lock, () => secondaryCaches.Get(key)));
}
}
return(results);
}