using System;
using System.Linq;
public class Program
{
public static void Main()
var nested = new [] {
new[] { 1, 2, 3},
new[] { 4, 5, 6},
new[] { 7, 8, 9}};
Console.WriteLine(nested.GetType());
Console.WriteLine(nested.SelectMany(t => t).ToArray().GetType());
}