using System;

using System.Collections.Generic;

using System.Diagnostics;

using System.Linq;

using System.Text.RegularExpressions;

​

namespace Playground

{

    public static class Program

    {

        private static readonly Regex Regex = new Regex("^[a-zA-Z0-9]*$", RegexOptions.Compiled);

        private static readonly Random Random = new Random();

        private static readonly Random MultipleRangeRandom = new Random();

        private static readonly Stopwatch Stopwatch = new Stopwatch();

​

        //49-57 = Numbers

        //65-90 = Uppercase

        //97-122 = Uppercase

        //32 = Space if you want to include it

        private static readonly List<Tuple<int,int>> MinMax = new List<Tuple<int, int>>()

        {

            new Tuple<int, int>(49, 57),

            new Tuple<int, int>( 65, 90 ),

            new Tuple<int, int>( 97, 122 )

        };

​

        public static void Main(string[] args)

        {

            // Pre-compile RegEx

             Regex.IsMatch(string.Empty);

             const int numberOfCharacters = 1000000;

             var alphaNum = new string(GenerateRandomAlphaNumericString(numberOfCharacters).ToArray());

             var anyChar = new string(GenerateRandomString(numberOfCharacters).ToArray());

             //Matches

            Console.WriteLine($" Using Regex: {ValidateStringRegex(alphaNum)}");

            Console.WriteLine($" Using For-Loop: {ValidateStringForLoop(alphaNum)}");

            Console.WriteLine($" Using Linq Extensions: {ValidateStringExpressions(alphaNum)}");

            //Non-Matches

            Console.WriteLine($" Using Regex: {ValidateStringRegex(anyChar)}");

            Console.WriteLine($" Using For-Loop: {ValidateStringForLoop(anyChar)}");

            Console.WriteLine($" Using Linq Extensions: {ValidateStringExpressions(anyChar)}");

        }

​

        private static IEnumerable<char> GenerateRandomString(int numberOfCharacters)

        {

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

            {

                yield return (char)Random.Next(0, 255);

            }

        }

​

        private static IEnumerable<char> GenerateRandomAlphaNumericString(int numberOfCharacters)

        {

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

            {

                var randomIndex = MultipleRangeRandom.Next(0, MinMax.Count);

                yield return (char)Random.Next(MinMax[randomIndex].Item1, MinMax[randomIndex].Item2);

            }

        }

​

        private static long ValidateStringRegex(string value)

        {

            Stopwatch.Restart();

            Regex.IsMatch(value);

            Stopwatch.Stop();

            return Stopwatch.ElapsedMilliseconds;

        }

​

        public static long ValidateStringForLoop(string value)

        {

            Stopwatch.Restart();

​

            if (string.IsNullOrEmpty(value))

            {

                Stopwatch.Stop();

                return Stopwatch.ElapsedMilliseconds;

            }

​

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

            {

                if (!char.IsLetter(value[i]) && !char.IsNumber(value[i]))

                {

                    Stopwatch.Stop();

                    return Stopwatch.ElapsedMilliseconds;

                }

            }

            Stopwatch.Stop();

            return Stopwatch.ElapsedMilliseconds;

        }

​

        public static long ValidateStringExpressions(IEnumerable<char> value)

        {

            Stopwatch.Restart();

​

            value.All(c => char.IsLetter(c) || char.IsNumber(c));

​

            Stopwatch.Stop();

            return Stopwatch.ElapsedMilliseconds;

        }

    }

}