Will the result of a LINQ query always be guaranteed to be in the correct order?

Question

Question: Will the result of a LINQ query always be guaranteed to be in the correct order?

Example:

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; 

var lowNums = 
  from n in numbers 
  where n < 5 
  select n; 

Now, when we walk through the entries of the query result, will it be in the same order as the input data numbers is ordered?

foreach (var x in lowNums) 
  { 
    Console.WriteLine(x); 
  } 

If someone can provide a note on the ordering in the documentation, this would be perfect.

Answer 1

• For LINQ to Objects: Yep.
• For Parallel LINQ: Nope.
• For LINQ to Expression Trees (EF, L2S, etc): Nope.