Airport Time Zones

Program.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
using GeoTimeZone; // Import from Nuget package "GeoTimeZone"  (https://github.com/mj1856/GeoTimeZone)
using TimeZoneConverter; // Import from Nuget package "TimeZoneConverter"  (https://github.com/mj1856/TimeZoneConverter)

namespace AirportTimeZones.DataBuilder
{
    class Program
    {
        static void Main(string[] args)
        {
            // Get the airports.csv data file from here: http://ourairports.com/data/

            using (var reader = File.OpenText("airports.csv"))
            {
                var header = reader.ReadLine();
                if (header == null)
                    return;

                var csvRegex = new Regex("((?<=\")[^\"]*(?=\"(,|$)+)|(?<=,|^)[^,\"]*(?=,|$))", RegexOptions.Compiled);

                var columns = csvRegex.Matches(header).Cast<Match>().Select((m, i) => new { m.Value, Index = i }).ToDictionary(x => x.Value, x => x.Index);
                var typeIndex = columns["type"];
                var latIndex = columns["latitude_deg"];
                var lonIndex = columns["longitude_deg"];
                var codeIndex = columns["iata_code"];

                var results = new Dictionary<string, string>();
                string[] badCodes = { "", "-", "---", "0" };

                string line;
                while ((line = reader.ReadLine()) != null)
                {
                    var values = csvRegex.Matches(line);

                    var type = values[typeIndex].Value;
                    var code = values[codeIndex].Value;

                    if (badCodes.Contains(code) || type == "closed" || results.ContainsKey(code))
                        continue;

                    var lat = Double.Parse(values[latIndex].Value);
                    var lon = Double.Parse(values[lonIndex].Value);
                    var tz = TimeZoneLookup.GetTimeZone(lat, lon).Result;

                    results.Add(code, tz);
                }

                using (var writer = File.CreateText("timezones.csv"))
                {
                    writer.WriteLine("\"iata_code\",\"iana_tz\",\"windows_tz\"");
                    foreach (var item in results.OrderBy(x => x.Key))
                    {
                        var windowsTimeZone = TZConvert.IanaToWindows(item.Value);
                        writer.WriteLine("\"{0}\",\"{1}\",\"{2}\"", item.Key, item.Value, windowsTimeZone);
                    }
                }
            }
        }
    }
}

timezones.csv