using System;

using System.Text;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string[] numbers = new []{"0654767491", "+31654767491","074 245 5290", "0031654767491",  "(074) 245 5290"};

        foreach (var number in numbers){

            Console.WriteLine("Number:" + number);

            Console.WriteLine("\told: " + OldMethod(number));

            Console.WriteLine("\tnew: " + NewMethod(number));

            Console.WriteLine("");

        }

    }

    public static long NewMethod (string phoneNumber)

    {

        var number = phoneNumber

            .RegexReplace("[^\\d]", "")

            .TrimStart('0');

        if (!number.StartsWith("31"))

        {

            number = string.Format("31{0}", number);

        }

        return number.TryParseLong(0);

    }

    public static long OldMethod (string phoneNumber)

    {

        var number = phoneNumber.Replace(" ", "").Replace("+", "").Replace("-", "").Trim();

        if (number.StartsWith("0"))

        {

            number = number.Substring(1, number.Length - 1);

        }

        if (!number.StartsWith("31"))

        {

            number = string.Format("31{0}", number);

        }

        return number.TryParseLong(0);

    }

​

}

​

​

    public static class ext {

        public static long TryParseLong(this string source, long defaultValue)

        {

            return source.TryParseLong() ?? defaultValue;

        }

​

        public static long? TryParseLong(this string source)

        {

            long result;

            return long.TryParse(source, out result)

                ? (long?)result

                : null;

        }

​

​

        public static string Replace(this string inputString, string oldValue, string newValue, StringComparison comparison)

        {

            var stringBuilder = new StringBuilder();

​

            int previousIndex = 0,

                index = inputString.IndexOf(oldValue, comparison);

​

            while (index != -1)

            {

                stringBuilder

                    .Append(inputString.Substring(previousIndex, index - previousIndex))

                    .Append(newValue);

​

                previousIndex = (index += oldValue.Length);

                index = inputString.IndexOf(oldValue, index, comparison);

            }

​

            stringBuilder.Append(inputString.Substring(previousIndex));

​

            return stringBuilder.ToString();

        }

​

​

        public static string RegexReplace(this string source, string regexPattern, string replace)

        {

            return RegexReplace(source, new Regex(regexPattern), c => replace);

        }

​

        public static string RegexReplace(this string source, Regex regex, string replace)

        {

            return regex.Replace(source, replace);

        }

​

        public static string RegexReplace(this string source, string regexPattern, MatchEvaluator matchEvaluator)

        {

            return RegexReplace(source, new Regex(regexPattern), matchEvaluator);

        }

​

        public static string RegexReplace(this string source, Regex regex, MatchEvaluator matchEvaluator)

        {

            return regex.Replace(source, matchEvaluator);

        }

​

    }