using System;

using System.Linq;

public class Program

{

    public static int HighestProductOf3(int[] arrayOfInts)

    {

        int arrayCount = arrayOfInts.Length;

        if (arrayCount < 3)

            throw new System.ArgumentException("Highest Product of 3 requires minimum of 3 ints to evaluate!");

        // Calculate the highest product of three numbers

        // sort arrayOfInts by order

        arrayOfInts = arrayOfInts.OrderBy(x => x).ToArray();

        int maxProduct = arrayOfInts[arrayCount - 1] * arrayOfInts[arrayCount - 2] * arrayOfInts[arrayCount - 3];

        if(arrayOfInts[0] < 0 && arrayOfInts[1] < 0 && arrayOfInts.Last() > 0)

            maxProduct = Math.Max(maxProduct, arrayOfInts[0] * arrayOfInts[1] * arrayOfInts.Last());

        return maxProduct;

    }

​

    public static void Main()

    {

        int maxProduct = HighestProductOf3(new int[] { -1, -2, -3, 10 });

        Console.WriteLine(maxProduct);

    }

}