String.Format Phone Numbers with Extension

Question

I am trying to create a an function that formats US phone numbers -- hopefully without looping through each digit.

When 10 digits are passed in all is fine. How ever when more than 10 digits are passed in I want the String.Format method to append the extension digits on the right. For example:

When 14 digits passed in the result should be:[phone] x8888 When 12 digits passed in the result should be:[phone] x88 etc. However what I get with my current attempt is: Passing in 12 digits returns this string '() -949 x555444433'

here is what I have so far.

public static string _FormatPhone(object phonevalue)
{
    Int64 phoneDigits;

    if (Int64.TryParse(phonevalue.ToString(), out phoneDigits))
    {
        string cleanPhoneDigits = phoneDigits.ToString();
        int digitCount = cleanPhoneDigits.Length;

        if (digitCount == 10)
            return String.Format("{0:(###) ###-####}", phoneDigits);
        else if (digitCount > 10)
            return String.Format("{0:(###) ###-#### x#########}", phoneDigits);
        else
            return cleanPhoneDigits;
    }

    return "Format Err#";
}

Thanks in advance.

Solution 1

I think you'll have to break your phoneDigits string into the first 10 digits and the remainder.

//[snip]
else if (phoneDigits.ToString().Length > 10)
        {
            return String.Format("{0:(###) ###-#### x}{1}", phoneDigits.Substring(0,10), phoneDigits.Substring(10) );
        }
//[snip]

Solution 2

Trying to squeeze it into 1 line, I came up with this.

var phoneNumber = "[phone] ext123";
phoneNumber = Regex.Replace(phoneNumber, "(.*?)([+]\\d{1,3})?(.*?)(\\d{3})(.*?)(\\d{3})(.*?)(\\d{4})([ ]+)?(x|ext)?(.*?)(\\d{2,5})?(.*?)$", "$2 $4 $6 $8 $10$12").Trim().Replace("ext","x");

If it starts with +# it will leave that alone. It will then look for blocks of numbers. 3,3,4 then it looks for ext or x for extension and another 2-5 numbers. At that point you can format it anyway you like, I chose spaces.

1234567890 -> '123 456 7890'

[phone] -> '123 456 7890'

[phone] ext123 -> '[phone] x123'

Solution 3

I'd suggest treating it as a string of digits, not a number. You would then use Substring explicitly to break out the parts.

Comments

[Steven Sudit]

I would consider regexp to be complete overkill for this example.

[Steven Sudit]

Ok, but if you're going to go down the Substring path, why stop there?

[Ahmad Mageed]

This doesn't handle the case where 10 digits are used and $4 is empty, which returns the result with a trailing "x": 312-588-2300 x

[BlackICE]

@Steven Why, a phone number is after all a regular expression?

[Ray]

@Ahmad - good point - I am editing my response with another regex approach, using a MatchEvaluator just to see how it works.

[ChiliYago]

This seems straight forward enough. else if (phoneDigitString.Length > 10) { return String.Format( "({0}) {1}-{2} x{3}", phoneDigitString.Substring(0, 3), phoneDigitString.Substring(3, 3), phoneDigitString.Substring(3, 4), phoneDigitString.Substring(10)); }

[Steven Sudit]

It's a safe bet that the Substring way would be faster.

[Steven Sudit]

@David: Because we have all the digits just sitting there. Nothing to search, nothing to match. All we need to do is mix them in with some formatting, and that's easy enough with a StringBuffer.

[kiev]

This works Chili, but what if you have a number like 18005551212? Can a valid phone number start with 1 in the US or is it always used like 1 [phone] ? or 1 [phone] ?