How do I change my new list without changing the original list?

Question

I have a list that gets filled in with some data from an operation and I am storing it in the memory cache. Now I want another list which contains some sub data from the li

Answer 1

Your are seeing the original list being modified because, by default, any non-primitive objects, are passed by reference (It is actually pass by value, the value being the reference, but that is a different matter).

What you need to do is clone the object. This question will help you with some code to clone a List in C#: How do I clone a generic list in C#?