using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var weights = new List<double>()

        {1.5, 18.5, 2.3, 6.3};

        var sumOfAllWeights = weights.Aggregate(0d, (sum, value) => sum + value);

        var rng = new Random();

        var howManyTimesPicked = Enumerable.Repeat(0, weights.Count).ToArray();

        for (var i = 0; i < 100; i++)

        {

            var randomNumber = rng.NextDouble() * sumOfAllWeights;

            var previousValue = 0d;

            var pickedIndex = 0;

            for (var currentIndex = 0; currentIndex < weights.Count; currentIndex++)

            {

                var currentWeight = weights[currentIndex];

                if (randomNumber > previousValue && randomNumber < previousValue + currentWeight)

                {

                    pickedIndex = currentIndex;

                }

​

                previousValue += currentWeight;

            }

​

            howManyTimesPicked[pickedIndex]++;

        // Console.WriteLine("Picked index " + pickedIndex);

        }

​

        Console.WriteLine("index : weight : picks");

        for (var i = 0; i < howManyTimesPicked.Length; i++)

        {

            Console.WriteLine(i + " : " + weights[i] + " : " + howManyTimesPicked[i]);

        }

    }

}