using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Valid Numbers");

        Console.WriteLine(IsValidPhone("847.555.1212"));

        Console.WriteLine(IsValidPhone("(847)555-1212"));

        Console.WriteLine(IsValidPhone("8475551212"));

        Console.WriteLine(IsValidPhone("847 555 1212"));

        Console.WriteLine(IsValidPhone("847-555-1212"));

        Console.WriteLine(IsValidPhone("1847-555-1212"));

        Console.WriteLine(IsValidPhone("+1847-555-1212"));

        Console.WriteLine(IsValidPhone("1847-555-1212 x123"));

        Console.WriteLine(IsValidPhone("847-555-1212 x123"));

        Console.WriteLine(IsValidPhone("3087774825"));

        Console.WriteLine(IsValidPhone("(281)388-0388"));

        Console.WriteLine(IsValidPhone("(281)388-0300"));

        Console.WriteLine(IsValidPhone("(979) 778-0978"));

        Console.WriteLine(IsValidPhone("(281)934-2479"));

        Console.WriteLine(IsValidPhone("(281)934-2447"));

        Console.WriteLine(IsValidPhone("(979)826-3273"));

        Console.WriteLine(IsValidPhone("(979)826-3255"));

        Console.WriteLine(IsValidPhone("(281)356-2530"));

        Console.WriteLine(IsValidPhone("(281)356-5264"));

        Console.WriteLine(IsValidPhone("(936)825-2081"));

        Console.WriteLine(IsValidPhone("(832)595-9500"));

        Console.WriteLine(IsValidPhone("(832)595-9501"));

        Console.WriteLine(IsValidPhone("281-342-2452"));

        Console.WriteLine("");

        Console.WriteLine("Invalid Numbers");

        Console.WriteLine(IsValidPhone("555-1212"));

        Console.WriteLine(IsValidPhone("1212"));

        Console.WriteLine(IsValidPhone("147-555-1212"));

        Console.WriteLine(IsValidPhone("133 443 1660"));

        Console.WriteLine(IsValidPhone("133 471 4149"));

        Console.WriteLine(IsValidPhone("1334431660"));

        Console.WriteLine(IsValidPhone("1334714149"));

    }

     public static bool IsValidPhone(string Phone)

    {

        try

        {

            if (string.IsNullOrEmpty(Phone))

                return false;

            var r = new Regex(@"((?:\(?[2-9](?(?=1)1[02-9]|(?(?=0)0[1-9]|\d{2}))\)?\D{0,3})(?:\(?[2-9](?(?=1)1[02-9]|\d{2})\)?\D{0,3})\d{4})");

            //var r = new Regex(@"\(?\d{3}\)?[-\.]? *\d{3}[-\.]? *[-\.]?\d{4}");

            return r.IsMatch(Phone);

​

        }

        catch (Exception)

        {

            throw;

        }

    }

}

​

​

​