Can I Format A String Like A Number in .NET?

Question

If I had a phone number like this

string phone = "6365555796";

Which I store with only numeric characters in my database (as a string), is it possible to output the number like this:

"636-555-5796"

Similar to how I could if I were using a number:

long phone = 6365555796;
string output = phone.ToString("000-000-0000");

I've tried searching and all I could find online were numeric formatting documents.

The reason I ask is because I think it would be an interesting idea to be able to store only the numeric values in the DB and allow for different formatting using a Constant string value to dictate how my phone numbers are formatted. Or am I better off using a number for this?

EDIT: The question is to format a string that contains numbers, not a number itself.

Answer 1

Why not just do something like this?

string phoneText = "6365555796";
long phoneNum = long.Parse(phoneText);
string output = phoneNum.ToString("000-000-0000");

Answer 2

You could potentially do a string insert at a given character point. Kinda like: phone = phone.Insert(3, "-"); phone = phone.Insert(7, "-");

Answer 3

To control string format of a number for display in an ASP.NET Gridview or another control, you can wrap your item in a helper class for display purposes:

public class PhoneDisplay
{
    long phoneNum;
    public PhoneDisplay(long number)
    {
        phoneNum = number;
    }
    public override string ToString()
    {
        return string.Format("{0:###-###-####}", phoneNum);
    }

}

Then, define data or display fields as (e.g.):

PhoneDisplay MyPhone = new PhoneDisplay(6365555796);

Answer 4

I think this works

string s = string.Format("{0:###-###-####}", ulong.Parse(phone));

In addtion, this http://blog.stevex.net/index.php/string-formatting-in-csharp/ is a nice post on formatting strings in .NET.

Thanks to @swilliams for clarifications.

Answer 5

Best I can think of without having to convert to a long/number and so it fits one line is:

string number = "1234567890";
string formattedNumber = string.Format("{0}-{1}-{2}", number.Substring(0,3), number.Substring(3,3), number.Substring(6));

Answer 6

Be aware that not everyone uses the North American 3-3-4 format for phone numbers. European phone numbers can be up to 15 digits long, with significant punctuation, e.g. +44-XXXX-XXXX-XXXX is different from 44+XXXX-XXXX-XXXX. You are also not considering PBXs and extensions, which can require over 30 digits.

Military and radio phones can have alphabetic characters, no this is not the "2" = "ABC" you see on touch-tone phones.

Answer 7

The simple version:

string phone = "6365555796";
Convert.ToInt64(phone).ToString("000-000-0000");

To wrap some validation around that and put it in a nice method:

string FormatPhone(string phone)
{
   /*assume the phone string came from the database, so we already know it's
     only digits.  If this changes in the future a simple RegEx can validate 
     (or correct) the digits requirement. */

   // still want to check the length:
   if (phone.Length != 10) throw new InvalidArgumentException();

  return Convert.ToInt64(phone).ToString("000-000-0000");
}

Answer 8

I loves me some extension method action:

   /// <summary>
   ///   Formats a string of nine digits into a U.S. phone number.
   /// </summary>
   /// <param name="value">
   ///   The string to format as a phone number.
   /// </param>
   /// <returns>
   ///   The numeric string as a U.S. phone number.
   /// </returns>
   public static string
   ToUSPhone (this string value)
   {
      if (value == null)
      {
         return null;
      }

      long  dummy;

      if ((value.Length != 10) ||
         !long.TryParse (
            value,
            NumberStyles.None,
            CultureInfo.CurrentCulture,
            out dummy))
      {
         return value;
      }

      return string.Format (
         CultureInfo.CurrentCulture,
         "{0}-{1}-{2}",
         value.Substring (0, 3),
         value.Substring (3, 3),
         value.Substring (6));
   }

Answer 9

Sure:

Regex.Replace(phone, @"^(\d{3})(\d{3})(\d{4})$", @"$1-$2-$3")

Of course, now you have 2 problems.