DistinctBy should allow a null comparer

[atifaziz]

Originally reported on Google Code with ID 3

What steps will reproduce the problem?

int[] source = { 1, 2, 3, 2, 1 };
source.DistinctBy(x => x, null);

What is the expected output? What do you see instead?

The expected output is { 1, 2, 3 } assuming the default comparer 
implementation since a null comparer is supplied. This would be consistent 
with the Enumerable.Distinct operator from Microsoft's base LINQ-to-
Objects implementation. However, what one sees instead is a 
ArgumentNullException from DistinctBy.

Reported by azizatif on 2009-02-15 18:58:27

[atifaziz]

Fixed in r5.

Reported by azizatif on 2009-02-15 19:01:23

• Status changed: Fixed