Question

I have an IEnumerable<MyObject> collection, with N MyObject elements.
MyObject is a class with a Title, a Description and an ID (as string).

I’d like to have my collection with distinct list of MyObject, due to the ID field.
So if 2 MyObject have got the same ID, one should be deleted (don’t care which, I need unique ID).

How can I do it with LINQ?

Tried :

myList = myList.GroupBy(o => o.ID); 

but seems I need a cast?

Answer 1

You can implement a custom IEqualityComparer<MyObject>. Then you can use Enumerable.Distinct to filter out duplicates.

class DistinctIdComparer : IEqualityComparer<MyObject> {
    public bool Equals(MyObject x, MyObject y) {
        return x.Id == y.Id;
    }

    public int GetHashCode(MyObject obj) {
        return obj.Id.GetHashCode();
    }
}

Now it’s simple:

IEnumerable<MyObject> distinct = myObjects.Distinct(new DistinctIdComparer());

Or you can use Enumerable.GroupBy what is even simpler:

distinct = myObjects.GroupBy(o => o.ID)
                    .Select(g => g.First());