c# linq - get elements from array which do not exist in a different array

Question

I have two arrays idxListResponse & _index both of which have the same structure.

Each of these arrays contains a number of elements with different properties on

Answer 1

Except is a good way of doing that:

var items = source1.Except(source2);

Would return all items in source1 except those in source2.

Since your collections appear to be different types, you would do something like:

source1.Except(source2.Select(s => /* selector here */))

Or you could create your own implementation of IEqualityComparer and use that to compare the two different types.