using System;
using System.Linq;
using System.Collections.Generic;
 
class LinqExercise
{
    static void Main(string[] args)
    {
 
        var arr = new[] { 6,7,8,9 };
 
        var sqaure = from int Number in arr
                   let SqrNo = Number * Number                   
                     select new { Number, SqrNo };
 
        foreach (var a in sqaure)
            Console.WriteLine(a);
 
        Console.ReadLine();
    }
}

Result