CONCAT

合并两个集合(不删除重复项)

List<int> foo = new List<int> { 1, 2, 3 };
List<int> bar = new List<int> { 3, 4, 5 };

// Through Enumerable static class
var result = Enumerable.Concat(foo, bar).ToList(); // 1,2,3,3,4,5

// Through extension method
var result = foo.Concat(bar).ToList(); // 1,2,3,3,4,5