Replacing substrings using Regex in C# .NET: phone number example

In this post we saw an application of Regex and Match to reformat date strings. Let’s check another example: change the following phone number formats…:

  • (xxx)xxx-xxxx: (123)456-7890
  • (xxx) xxx-xxxx: (123) 456-7890
  • xxx-xxx-xxxx: 123-456-7890
  • xxxxxxxxxx: 1234567890

…into (xxx) xxx-xxxx.

Here’s a possible solution:

private static string ReformatPhone(string phone)
	Match match = Regex.Match(phone, @"^\(?(\d{3})\)?[\s\-]?(\d{3})\-?(\d{4})$");
	return string.Format("({0}) {1}-{2}", match.Groups[1], match.Groups[2], match.Groups[3]);

If you call this function with any of the above 4 examples it will return “(123) 456-7890”.

View all posts related to string and text operations here.


About Andras Nemes
I'm a .NET/Java developer living and working in Stockholm, Sweden.

One Response to Replacing substrings using Regex in C# .NET: phone number example

  1. Serg says:

    I’m not sure whether this link is still alive, but just in case.

    I have a problem with Swedish Phone numbers validation – Can’t find a Regex working properly with the following Swedish phones ( given as a samples) below:
    +46 8 123 456
    78 0123-456 78
    08 791 4400
    +46 08 791 4400

    Do you know the solution?
    Is it possible that the phones are incorrect?


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