.Net STUFF's - Guide to get it..

var result = list1.Concat(list2);
ListaddedList = result.ToList();

List list1 = new List();
list1.Add("One");
list1.Add("Two");

List list2 = new List();
list2.Add("three");
list2.Add("four");

var result = list1.Concat(list2);
List addedList = result.ToList();