using Microsoft.Extensions.DependencyInjection;

using Microsoft.Extensions.Logging;

using System;

using System.Collections.Generic;

using System.Diagnostics;

using System.Threading.Tasks;

​

namespace ConsoleApp1

{

    public class Program

    {

        public static async Task Main()

        {

            var container = new ServiceCollection();

            container.AddLogging(b => b.AddConsole());

​

            using (var scope = container.BuildServiceProvider().CreateScope())

            {

                var sp = scope.ServiceProvider;

                var logger = sp.GetRequiredService<ILogger<Program>>();

​

                var doubles = new List<double> { 1.23, 68.256, 44.55, 96.127, 393.4567, 2.45, 4.1 };

​

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

                {

                    var timer1 = Stopwatch.StartNew();

                    var avg1 = doubles.Average<double>();

                    timer1.Stop();

​

                    var timer2 = Stopwatch.StartNew();

                    var avg2 = doubles.Average();

                    timer2.Stop();

​

                    logger.LogInformation("Without type: {0} [ticks={1}]", avg1, timer1.Elapsed.Ticks);

                    logger.LogInformation("Fixed type: {0} [ticks={1}]", avg2, timer2.Elapsed.Ticks);

                }

            }

            Console.WriteLine("Working...");

        }

​

​

    }

​

    public static class Extensions

    {

        public static double Average<T>(this IEnumerable<T> source)

        {

            if (source == null)

            {

                throw new ArgumentNullException(nameof(source));

            }

​

            double sum = 0;

            long count = 0;

            checked

            {

                foreach (T v in source)

                {

                    sum += Convert.ToDouble(v);

                    count++;

                }

            }

            if (count == 0)

            {

                return 0;

            }

            return (double)sum / count;

        }

​

        public static double Average(this IEnumerable<double> source)

        {

            if (source == null)

            {

                throw new ArgumentNullException(nameof(source));

            }

            double sum = 0;

            long count = 0;

            checked

            {

                foreach (double v in source)

                {

                    sum += v;

                    count++;

                }

            }

            if (count == 0)

            {

                return 0;

            }

            return sum / count;

        }

    }

}