use Concat with array elements

   
 
using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Linq;

public class MainClass{
   public static void Main(){
       int[] numbers = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
       int[] moreNumbers = { 10, 11, 12, 13 };

       var query = numbers.Concat(moreNumbers);
   }
}