using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        double latitude = 34.05072;

        double longitude = -118.25477;

        List<City> cities = new List<City>();

        cities.Add(new City() { 

            CityCode = "BUR",

            Latitude = 34.188,

            Longitude = -118.3234

        });

        cities.Add(new City() { 

            CityCode = "LAX",

            Latitude = 34.0673431844741,

            Longitude = -118.276097656207

        });

         var nearestCity = cities.GroupBy(x => Math.Pow((latitude - x.Latitude), 2) + Math.Pow((longitude - x.Longitude), 2))

                                      .OrderBy(x => x.Key)

                                      .First();

        Console.WriteLine(nearestCity.First().CityCode);

    }

}

​

public class City

{

    public string CityCode { get; set; }

    public double Latitude { get; set; }

    public double Longitude { get; set; }

}