using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

​

​

    public class Program

{

    public static void Main()

    {

         String testString = "method";

​

            Console.WriteLine(testString.CapitalizeFirstLetter().Pluralize());

​

            int a = 100;

            decimal b = 100.5M;

​

            Console.WriteLine(a.ApplyVAT());

            Console.WriteLine(b.ApplyVAT());

    }

}

​

public static class Extensions

{

     public static bool FirstLetterCapital(this string value)

        {

            if (string.IsNullOrEmpty(value))

            {

                return false;

            }

​

            return char.IsUpper(value[0]);

        }

​

        public static string Pluralize(this string value)

        {

            if (string.IsNullOrEmpty(value))

            {

                throw new NullReferenceException("Input can not be null or empty");

            }

​

            return value + "s";

        }

​

        public static string CapitalizeFirstLetter(this string value)

        {

            if (string.IsNullOrEmpty(value))

            {

                throw new NullReferenceException("Input can not be null or empty");

            }

​

            if (!value.FirstLetterCapital())

            {

                return char.ToUpper(value[0]) + value.Substring(1);

            }

​

            return value;

        }

​

        public static int CharacterCount(this string value)

        {

            if (value == null)

                return 0;

            return value.Length;

        }

        public static decimal ApplyVAT(this decimal value)

            {

            return value + 24 * value / 100;

        }

​

        public static int ApplyVAT(this int value)

        {

            return value + 24 * value / 100;

        }

}