Linq All on empty collection

Question

I need to check if all definitions contains some specific data. It works fine except the case when GroupBy returns empty collection.

var exist = dbContext.De         


        

Answer 1

Here's the alternative to All that returns false if collection is empty:

var collection = Enumerable.Range(0, 0); //empty collection

collection
  .Select(IsValid)
  .DefaultIfEmpty(false)
  .All(b => b);

Or as an extension method:

public static bool AnyAndAll(IEnumerable collection, Func predicate) =>
  collection
    .Select(predicate)
    .DefaultIfEmpty(false)
    .All(b => b);