How to unite two List<T> and assign result to the third List<T>?

Question

I have 3 List<> objects.

List<T> listA = new List<t>();
List<T> listB = new List<t>();
List<T> listC = new List<t>();

I need to unite listA and ListB and assign it to ListC:

List<T> listC = new ListA +ListB;

My question is how to implement it?

Answer 1

    List<int> A = new List<int>();
    A.Add(1);
    A.Add(2);
    List<int> B = new List<int>();
    B.Add(3);
    B.Add(4);

    List<int> C = new List<int>();

    C = A.Union<int>(B).ToList<int>();

Answer 2

Use AddRange:

List<T> listA = new List<t>();
List<T> listB = new List<t>();
List<T> listC = new List<t>();

listC.AddRange(listA);
listC.AddRange(listB);