Is there a "not equal" in a linq join
No, a "not equal" operator would get you all combinations of groupA and groupB except the ones where the items were the same.
Using the Except method gets you what you want:
var filteredEmployees = groupA.Except(groupB);
You don't need a join for that:
var filteredEmployees = groupA.Except(groupB);
Note that this will be a sequence of unique employees - so if there are any duplicates in groupA
, they will only appear once in filteredEmployees
. Of course, it also assumes you've got a reasonable equality comparer1. If you need to go specifically on name, you can use ExceptBy
from MoreLINQ:
var filteredEmployees = groupA.ExceptBy(groupB, employee => employee.Name);
Or without going into a third party library:
var groupBNames = new HashSet<string>(groupB.Select(x => x.Name));
var filteredEmployees = groupA.Where(x => !groupBNames.Contains(x.Name));
1 As pointed out in the comments, you can pass in an IEqualityComparer<T>
as an argument to Except
. I have a ProjectionEqualityComparer
class in MiscUtil which makes it easy to build a comparer of the kind you need:
// I can't remember the exact method name, but it's like this :)
var comparer = ProjectionEqualityComparer<Employee>.Create(x => x.Name);
var filteredEmployees = groupA.Except(groupB, comparer);