Haversine C#

Position pos1 = new Position();
pos1.Latitude = 40.7486;
pos1.Longitude = -73.9864;
 
Position pos2 = new Position();
pos2.Latitude = 24.7486;
pos2.Longitude = -72.9864;
 
Haversine hv = new Haversine();
double result = hv.Distance(pos1, pos2, DistanceType.Kilometers);

Here is the code for the class:
using System;
 
namespace HaversineFormula
{
    /// <summary>
    /// The distance type to return the results in.
    /// </summary>
    public enum DistanceType { Miles, Kilometers };
 
    /// <summary>
    /// Specifies a Latitude / Longitude point.
    /// </summary>
    public struct Position
    {
        public double Latitude;
        public double Longitude;
    }
 
    class Haversine
    {
        /// <summary>
        /// Returns the distance in miles or kilometers of any two
        /// latitude / longitude points.
        /// </summary>
        /// <param name=”pos1″></param>
        /// <param name=”pos2″></param>
        /// <param name=”type”></param>
        /// <returns></returns>
        public double Distance(Position pos1, Position pos2,DistanceType type)
        {
            double R = (type == DistanceType.Miles) ? 3960 : 6371;
 
            double dLat = this.toRadian(pos2.Latitude – pos1.Latitude);
            double dLon = this.toRadian(pos2.Longitude – pos1.Longitude);
 
            double a = Math.Sin(dLat / 2) * Math.Sin(dLat / 2) +
                Math.Cos(this.toRadian(pos1.Latitude)) *Math.Cos(this.toRadian(pos2.Latitude)) *
                Math.Sin(dLon / 2) * Math.Sin(dLon / 2);
            double c = 2 * Math.Asin(Math.Min(1, Math.Sqrt(a)));
            double d = R * c;
 
            return d;
        }
 
        /// <summary>
        /// Convert to Radians.
        /// </summary>
        /// <param name=”val”></param>
        /// <returns></returns>
        private double toRadian(double val)
        {
            return (Math.PI / 180) * val;
        }
    }
}

Awesome script, helped me with an ArcGIS Unity SDK project. Simple as well.

An small efficiency tweak is to us the earth diameter (2 times the R in the code above) instead of R and eliminate the 2 * on line 52

So like
double D = InKillometers == DistanceType.Kilometers ? 12742 : 7918; // Earth diameter

and then

double distanceMiles = D * c;