using System;

using System.Linq;

using System.Collections.Generic;

using System.Diagnostics;

​

public class Program {

    public static void Main() {

        var list = "1,2,4";

        var nums = list

            .Split(',')

            .Select(i => 

            { 

                int val;

                return int.TryParse(i, out val) ? (int?)val : null;

            })

            .Where(i => i.HasValue)

            .Cast<int>();

        foreach(int number in nums)

        {

            Console.WriteLine(number);

        }

    }

}