Linq-to-entities to normal linq

Question

I have this line of linq

_cache = _repository.EntitiesNoTracking().Select(k => Crypto.DecryptString(k.KeyValue)).ToHashSet();

This of course doesn't work, as Linq-to-entities doens't know Crypto.DecryptString. So the solution could be

_cache = _repository.EntitiesNoTracking().ToArray().Select(k => Crypto.DecryptString(k.KeyValue)).ToHashSet();

However, this seems to have a redundant ToArray() in there. I supposed the next code would be more efficient:

var _cache = new HashSet<string>();
foreach(var item in _repository.EntitiesNoTracking()){
    _cache.Add(Crypto.DecryptString(item.KeyValue));
}

Isn't there some way of telling Linq-to-entities to convert to normal linq, without the extra step?

Answer 1

You do not need EntitiesNoTracking() because you have custom projection. Also retrieved data should be limited by additional Select.

_cache = _repository.
   .Select(k => k.KeyValue)
   .AsEnumerable()
   .Select(s => Crypto.DecryptString(s))
   .ToHashSet();