using System;

using System.Collections.Generic;

using System.Collections.ObjectModel;

using System.Diagnostics;

using System.Linq;

public class Program

{

    public static void Main()

    {

        int loops = 1000000;

​

            string[] array = new string[loops];

            for (int i = 0; i < loops; i++)

            {

                array[i] = "s";

            }

​

            List<string> list = new List<string>();

            for (int i = 0; i < loops; i++)

            {

                list.Add("s");

            }

​

            IEnumerable<string> enumerableSelect = list.Select(t => t);

            IReadOnlyCollection<string> readOnlyCollection = new ReadOnlyCollection<string>(list);

​

            Stopwatch sw = new Stopwatch();

            Stopwatch(array);

            Stopwatch(list);

            Stopwatch(enumerableSelect);

            Stopwatch(readOnlyCollection);

            void Stopwatch(IEnumerable<string> strings)

            {

                sw.Restart();

                for (int i = 0; i < loops; i++)

                {

                    strings.NullOrEmpty();

                }

​

                sw.Stop();

                Console.WriteLine($"{strings.GetType()} Any " + sw.Elapsed);

​

                sw.Restart();

                for (int i = 0; i < loops; i++)

                {

                    array.NullOrEmptyCount();

                }

​

                sw.Stop();

                Console.WriteLine($"{strings.GetType()} Count " + sw.Elapsed);

​

                sw.Restart();

                for (int i = 0; i < loops; i++)

                {

                    array.NullOrEmptyIfs();

                }

​

                sw.Stop();

                Console.WriteLine($"{strings.GetType()} Ifs " + sw.Elapsed);

            }

    }

}

​

    public static class EnumerableExtensions

    {

        public static bool NullOrEmpty<T>(this IEnumerable<T> enumerable) =>

            enumerable == null || !enumerable.Any();

​

        public static bool NullOrEmptyCount<T>(this IEnumerable<T> enumerable) =>

            enumerable == null || enumerable.Count() == 0;

​

        public static bool NullOrEmptyIfs<T>(this IEnumerable<T> enumerable)

        {

            if (enumerable is null)

            {

                return true;

            }

​

            if (enumerable is ICollection<T> collection)

            {

                return collection.Count == 0;

            }

​

            return enumerable.Any();

        }

​

        public static bool NotNullAndAny<T>(this IEnumerable<T> enumerable) =>

            !enumerable.NullOrEmpty();

​

        public static bool NotNullAndAny<T>(this IEnumerable<T> enumerable, Func<T, bool> predicate) => enumerable?.Any(predicate) ?? false;

    }