Concat in LINQ

Suppose we have two list of numbers and they are:

var numberList1 = new List<int>{3, 4, 5, 6, 7};
var numberList2 = new List<int>{21, 3, 5, 23, 4};

Now we want to concat this two list of numbers using LINQ. Then our code will be

namespace linqTut
{
    class Program
    {
        static void Main(string[] args)
        {
            var numberList1 = new List<int>{3, 4, 5, 6, 7};
            var numberList2 = new List<int>{21, 3, 5, 23, 4};
            var resultList = numberList1.Concat(numberList2);
            foreach (var i in resultList)
            {
                Console.Write(i + " ");
            }
        }
    }
}

And the output will be:
3 4 5 6 7 21 3 5 23 4