What does LINQ return when the results are empty

Question

I have a question about LINQ query. Normally a query returns a IEnumerable type. If the return is empty, not sure if it is null or not. I am not sure if the following ToList() will throw an exception or just a empty List<string> if nothing found in IEnumerable result?

   List<string> list = {"a"};
   // is the result null or something else?
   IEnumerable<string> ilist = from x in list where x == "ABC" select x;
   // Or directly to a list, exception thrown?
   List<string> list1 = (from x in list where x == "ABC" select x).ToList();

I know it is a very simple question, but I don't have VS available for the time being.

Answer 1

It will return an empty enumerable. It wont be null. You can sleep sound :)

Answer 2

.ToList returns an empty list. (same as new List() );

Answer 3

It won't throw exception, you'll get an empty list.

Answer 4

var lst = new List<int>() { 1, 2, 3 };
var ans = lst.Where( i => i > 3 );

(ans == null).Dump();  // False
(ans.Count() == 0 ).Dump();  // True

(Dump is from LinqPad)

Answer 5

Other posts here have made it clear that the result is an "empty" IQueryable, which ToList() will correctly change to be an empty list etc.

Do be careful with some of the operators, as they will throw if you send them an empty enumerable. This can happen when you chain them together.

Answer 6

In Linq-to-SQL if you try to get the first element on a query with no results you will get sequence contains to elements error. I can assure you that the mentioned error is not equal to object reference not set to an instance of an object. in conclusion no, it won't return null since null can't say sequence contains to elements it will always say object reference not set to an instance of an object ;)