phtest.cs

    [TestClass]
    public class UnitTest1
    {
        [TestMethod]
        public void TestMethod1()
        {
            String s1 = TAMSLib.PhoneNumber.FormatUSA("5031234567");
            String s2 = TAMSLib.PhoneNumber.FormatUSA("1(503)1234567");
        }
    }

    public class PhoneNumber
    {
        static public string FormatUSA(string input)
        {
            StringBuilder sb = new StringBuilder();
            string rv = "";

            foreach (var c in input)
            {
                if ("0123456789".IndexOf(c) >= 0)
                {
                    sb.Append(c);
                }
            }
            if (sb.Length == 10)
            {
                rv = string.Format("({0}{1}{2}) {3}{4}{5}-{6}{7}{8}{9}", sb[0], sb[1], sb[2], sb[3], sb[4], sb[5], sb[6], sb[7], sb[8], sb[9]);
            }
            if (sb.Length == 11)
            {
                rv = string.Format("+{0} ({1}{2}{3}) {4}{5}{6}-{7}{8}{9}{10}", sb[0], sb[1], sb[2], sb[3], sb[4], sb[5], sb[6], sb[7], sb[8], sb[9], sb[10]);
            }
            return rv;
        }
    }