Remove formatting from a string: "(123) 456-7890" => "1234567890"?

Question

I have a string when a telephone number is inputted - there is a mask so it always looks like "(123) 456-7890" - I'd like to take the formatting out before saving it to the DB.

How can I do that?

Answer 1

One possibility using linq is:

string justDigits = new string(s.Where(c => char.IsDigit(c)).ToArray());

Answer 2

You could use a regular expression or you could loop over each character and use char.IsNumber function.

Answer 3

You can make it work for that number with the addition of a simple regex replacement, but I'd look out for higher initial digits. For example, (876) 543-2019 will overflow an integer variable.

Answer 4

You would be better off using regular expressions. An int by definition is just a number, but you desire the formatting characters to make it a phone number, which is a string.

There are numerous posts about phone number validation, see http://stackoverflow.com/questions/123559/a-comprehensive-regex-for-phone-number-validation for starters.

Answer 5

You can use a regular expression to remove all non-digit characters:

string phoneNumber = "(123) 456-7890";
phoneNumber = Regex.Replace(phoneNumber, @"[^\d]", "");

Then further on - depending on your requirements - you can either store the number as a string or as an integer. To convert the number to an integer type you will have the following options:

// throws if phoneNumber is null or cannot be parsed
long number = Int64.Parse(phoneNumber, NumberStyles.Integer, CultureInfo.InvariantCulture);

// same as Int64.Parse, but returns 0 if phoneNumber is null
number = Convert.ToInt64(phoneNumber);

// does not throw, but returns true on success
if (Int64.TryParse(phoneNumber, NumberStyles.Integer, 
       CultureInfo.InvariantCulture, out number))
{
    // parse was successful
}

Answer 6

Try this:

string s = "(123) 456-7890";
UInt64 i = UInt64.Parse(
    s.Replace("(","")
     .Replace(")","")
     .Replace(" ","")
     .Replace("-",""));

You should be safe with this since the input is masked.

Answer 7

string digits = Regex.Replace(formatted, @"\D", String.Empty, RegexOptions.Compiled);

Answer 8

As many answers already mention, you need to strip out the non-digit characters first before trying to parse the number. You can do this using a regular expression.

Regex.Replace("(123) 456-7890", @"\D", String.Empty) // "1234567890"

However, note that the largest positive value int can hold is 2,147,483,647 so any number with an area code greater than 214 would cause an overflow. You're better off using long in this situation.

Leading zeros won't be a problem for North American numbers, as area codes cannot start with a zero or a one.

Answer 9

Alternative using Linq:

string phoneNumber = "(403) 259-7898";
var phoneStr = new string(phoneNumber.Where(i=> i >= 48 && i <= 57).ToArray());

Answer 10

Since nobody did a for loop.

long GetPhoneNumber(string PhoneNumberText)
{
    // Returns 0 on error

    StringBuilder TempPhoneNumber = new StringBuilder(PhoneNumberText.Length);
    for (int i=0;i<PhoneNumberText.Length;i++)
    {
        if (!char.IsDigit(PhoneNumberText[i]))
            continue;

        TempPhoneNumber.Append(PhoneNumberText[i]);
    }

    PhoneNumberText = TempPhoneNumber.ToString();
    if (PhoneNumberText.Length == 0)
        return 0;// No point trying to parse nothing

    long PhoneNumber = 0;
    if(!long.TryParse(PhoneNumberText,out PhoneNumber))
        return 0; // Failed to parse string

    return PhoneNumber;
}

used like this:

long phoneNumber = GetPhoneNumber("(123) 456-7890"); 

Update
As pr commented many countries do have zero's in the begining of the number, if you need to support that, then you have to return a string not a long. To change my code to do that do the following:

1) Change function return type from long to string.
2) Make the function return null instead of 0 on error
3) On successfull parse make it return PhoneNumberText

Answer 11

Aside from all of the other correct answers, storing phone numbers as integers or otherwise stripping out formatting might be a bad idea.

Here are a couple considerations:

• Users may provide international phone numbers that don't fit your expectations. See these examples So the usual groupings for standard US numbers wouldn't fit.
• Users may NEED to provide an extension, eg (555) 555-5555 ext#343 The # key is actually on the dialer/phone, but can't be encoded in an integer. Users may also need to supply the * key.
• Some devices allow you to insert pauses (usually with the character P), which may be necessary for extensions or menu systems, or dialing into certain phone systems (eg, overseas). These also can't be encoded as integers.

[EDIT]

It might be a good idea to store both an integer version and a string version in the database. Also, when storing strings, you could reduce all punctuation to whitespace using one of the methods noted above. A regular expression for this might be:

// (222) 222-2222 ext# 333   ->   222 222 2222 # 333
phoneString = Regex.Replace(phoneString, @"[^\d#*P]", " ");

// (222) 222-2222 ext# 333   ->   2222222222333 (information lost)
phoneNumber = Regex.Replace(phoneString, @"[^\d]", "");

// you could try to avoid losing "ext" strings as in (222) 222-2222 ext.333 thus:
phoneString = Regex.Replace(phoneString, @"ex\w+", "#");
phoneString = Regex.Replace(phoneString, @"[^\d#*P]", " ");

Answer 12

This is basically a special case of http://stackoverflow.com/questions/1329961/c-removing-common-invalid-characters-from-a-string-improve-this-algorithm/. Where your formatng incl. White space are treated as "bad characters"

Answer 13

An answer from simpler times, by a man with a ton of simple, one might even say simple-ton:

    public static string Strip(this string phoneNumber)
    {
        return new string(
            new[]
                {
                 // phoneNumber[0],     (
                    phoneNumber[1],  // 6
                    phoneNumber[2],  // 1
                    phoneNumber[3],  // 7
                 // phoneNumber[4],     )
                 // phoneNumber[5],   
                    phoneNumber[6],  // 8
                    phoneNumber[7],  // 6
                    phoneNumber[8],  // 7
                 // phoneNumber[9],     -
                    phoneNumber[10], // 5
                    phoneNumber[11], // 3
                    phoneNumber[12], // 0
                    phoneNumber[13]  // 9
                });
    }

Performance should be spicy yet fresh.