using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public class Stock

    {

        public int Id { get; set; }

        public int? Yellow { get; set; }

        public int? Red { get; set; }

        public int? White { get; set; }

    }

    public static void Main()

    {

        List<Stock> list = new List<Stock>();

        list.Add(new Stock(){Id=1, Yellow = 50, Red = 0, White = 205});

        list.Add(new Stock(){Id=2, Yellow = 20, Red = 200, White = 35});

        list.Add(new Stock(){Id=3, Yellow = 0, Red = 100, White = 155});

        string ColumnName = "Yellow";

        var Test1 = GetColumnValue(list.Where(m=>m.Id == 1).ToList(), ColumnName);

        var Test2 = GetColumnValue(list.Where(m=>m.Id == 2).ToList(), ColumnName);

        var Test3 = GetColumnValue(list.Where(m=>m.Id == 3).ToList(), ColumnName);

        Console.WriteLine(Test1);

        Console.WriteLine(Test2);

        Console.WriteLine(Test3);

    }

    public static object GetColumnValue(List<Stock> items, string columnName)

    {

        var values = items.Select(x => x.GetType().GetProperty(columnName).GetValue(x)).FirstOrDefault();

        return values;

    }

}