Вы можете сделать это, используя Join
как
public class Program
{
static void Main(string[] args)
{
List<string> firstList = new List<string> { "A", "B" };
List<string> secondList = new List<string> { "C", "D", "E" };
List<string> thirdList = new List<string> { "F", "G" };
List<string> result = firstList
.Join(secondList, x => true, y => true, (m, n) => m + n)
.Join(thirdList, a => true, b => true, (a, b) => a + b)
.ToList();
result.ForEach(x => Console.WriteLine(x));
Console.ReadLine();
}
}
Выход:
