return whether any two numbers from the list add up to k, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Microsoft (R) Visual C# Compiler version 2.9.0.63208 (958f2354)

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

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            /*
            This problem was recently asked by Google.
            Given a list of numbers and a number k, return whether any two numbers from the list add up to k.
            For example, given [10, 15, 3, 7] and k of 17, return true since 10 + 7 is 17.
            Bonus: Can you do this in one pass?
            */
            var numbers=new[]{10,15,3,7};
            var k=17;

var additive = FindAdditives(numbers,k);

if(additive==null){
                Console.WriteLine($"Additive not found for {k}");
                return;
            }

Console.WriteLine($"Found two numbers {additive.OP1} and {additive.OP2} that adds to {k}");

}

public static Additives FindAdditives(int[] numbers, int k){

var hashSet=new HashSet<int>();

foreach(var num in numbers){

var op1=num;
                var op2= Math.Abs(k-num);

if(hashSet.Contains(op2))
                    return new Additives(op1,op2);

hashSet.Add(op2);
            }

return null;

}

public class Additives
    {

public Additives(int op1, int op2)
         {
           OP1=op1;
           OP2=op2;
         }

public int OP1{get;}
          public int OP2{get;}

}
}

Show compiler warnings [ + ] Show input
Compilation time: 0,28 sec, absolute running time: 0,09 sec, cpu time: 0,09 sec, average memory usage: 14 Mb, average nr of threads: 3, absolute service time: 0,42 sec