C# – Converting a normalized phone number to a user-friendly version

cformattingphone-numberregex

In my C# application, I use a regular expression to validate the basic format of a US phone number to make sure that the user isn't just entering bogus data. Then, I strip out everything except numbers, so this:

(123) 456-7890 x1234

becomes

12345678901234

in the database. In various parts of my application, however, I would like to convert this normalized phone number back to

(123) 456-7890 x1234

What's the best way to do such a thing? (Don't worry about accounting for international phone number formats, by the way.)

Best Answer

String.Format("{0:(###) ###-#### x ###}", double.Parse("1234567890123"))

Will result in (123) 456-7890 x 123

Related Solutions

C# – Phone Number Formatting, OnBlur

A fairly simple-minded approach would be to use a regular expression. Depending on which type of phone numbers you're accepting, you could write a regular expression that looks for the digits (for US-only, you know there can be 7 or 10 total - maybe with a leading '1') and potential separators between them (period, dash, parens, spaces, etc.).

Once you run the match against the regex, you'll need to write the logic to determine what you actually got and format it from there.

EDIT: Just wanted to add a very basic example (by no means is this going to work for all of the examples you posted above). Geoff's suggestion of stripping non-numeric characters might help out a bit depending on how you write your regex.

Regex regex = new Regex(@"(?<areaCode>([\d]{3}))?[\s.-]?(?<leadingThree>([\d]{3}))[\s.-]?(?<lastFour>([\d]{4}))[x]?(?<extension>[\d]{1,})?");
string phoneNumber = "701 123-4567x324";

Match phoneNumberMatch = regex.Match(phoneNumber);
if(phoneNumberMatch.Success)
{
   if (phoneNumberMatch.Groups["areaCode"].Success)
   {
      Console.WriteLine(phoneNumberMatch.Groups["areaCode"].Value);
   }
   if (phoneNumberMatch.Groups["leadingThree"].Success)
   {
      Console.WriteLine(phoneNumberMatch.Groups["leadingThree"].Value);
   }
   if (phoneNumberMatch.Groups["lastFour"].Success)
   {
      Console.WriteLine(phoneNumberMatch.Groups["lastFour"].Value);
   }
   if (phoneNumberMatch.Groups["extension"].Success)
   {
      Console.WriteLine(phoneNumberMatch.Groups["extension"].Value);
   }
}

Android – Programmatically obtain the phone number of the Android phone

Code:

TelephonyManager tMgr = (TelephonyManager)mAppContext.getSystemService(Context.TELEPHONY_SERVICE);
String mPhoneNumber = tMgr.getLine1Number();

Required Permission:

<uses-permission android:name="android.permission.READ_PHONE_STATE"/>

Caveats:

According to the highly upvoted comments, there are a few caveats to be aware of. This can return null or "" or even "???????", and it can return a stale phone number that is no longer valid. If you want something that uniquely identifies the device, you should use getDeviceId() instead.

Best Answer

Related Solutions

C# – Phone Number Formatting, OnBlur

Android – Programmatically obtain the phone number of the Android phone

Caveats:

Related Topic