LINQ Comparing Two Lists - Add new, remove old, leave the ones in common

Question

I have two lists (L1,L2) of an object A, L1 is used to store the list of objects(many to many relationship) before they are changed. L2 is the relationship after it has been changed. I need to keep the common elements but add the new ones and remove the ones that aren't in L2. I was wondering if there was a one liner I could use with LINQ to accomplish this. If you need more information just let me know.

Thanks in advance

Answer 1

If I understood your requirements correctly, this should work:

L1.AddRange(L2.Except(L1));
L1.RemoveAll(item => !L2.Contains(item));

Not a one-liner, but close enough...

Answer 2

try something like this

var a = from ele in list1
        let alleles = list1.Union(list2)
        let deleles = alleles.Except(list1)
        let neweles = alleles.Except(list2)
        select new { DeletedEles = deleles, NewEles = neweles };

Answer 3

Perhaps I'm misunderstanding, but isn't what you are asking for the set of objects that are stored in L2?

To use a concrete example, if you have these inputs:

L1: { 1, 2, 3, 4, 5 }
L2: { 2, 3, 5, 7 }

Isn't the desired result { 2, 3, 5, 7 }?

Answer 4

Maybe Linq's boolean operators like Intersect() could be of help to you?