How to take a phone number with a plus and bracket and just return the numbers?

Question

Hey Everyone,

I have a simple problem I have a phone like this: +1 (123) 123-1234 and I want to just take the numbers out of that string using regex. Any help will be greatly appreciated.

Thanks

Answer 1

This will strip out an non-numeric characters:

string input = "+1 (123) 123-1234";
string digits = Regex.Replace(input,@"\D",string.Empty);

Answer 2

Why not just do a replace?

string phoneNumber = "+1 (123) 123-1234";
phoneNumber = phoneNumber.Replace("+", "");
phoneNumber = phoneNumber.Replace("(", "");
phoneNumber = phoneNumber.Replace(")", "");
phoneNumber = phoneNumber.Replace("-", "");
phoneNumber = phoneNumber.Replace(" ", "");

Answer 3

string digits = Regex.Replace(input, @"[^\d]", String.Empty);

Answer 4

Using RegEx is one solution. Another way would be to use LINQ (provided you are using .Net 3.5)

    string myPhone = "+1 (123) 123-1234";
    string StrippedPhone = new string((from c in myPhone
                                       where Char.IsDigit(c)
                                       select c).ToArray());

The end result is the same, but I think LINQ offers some advantages over RegEx in this case. First, readability. The RegEx requires you to know that "D" means Non digit (compared to Char.IsDigit())- there is confusion about that already in the comments here. Also, I did a very simple benchmark, performing each method 100,000 times.

LINQ: 127ms

RegEx: 485ms

So, at a quick glance, it seems like LINQ out performs Regex in this situation. And, I'd argue it is more readable.

    int i;
    int TIMES = 100000;
    Stopwatch sw = new Stopwatch();
    string myPhone = "+1 (123) 123-1234";

    // Using LINQ            
    sw.Start();
    for (i = 0; i < TIMES; i++)
    {
        string StrippedPhone = new string((from c in myPhone
                                           where Char.IsDigit(c)
                                           select c).ToArray());
    }
    sw.Stop();
    Console.WriteLine("Linq took {0}ms", sw.ElapsedMilliseconds);

    // Reset 
    sw.Reset();

    // Using RegEx
    sw.Start();
    for (i = 0; i < TIMES; i++)
    {
        string digits = Regex.Replace(myPhone, @"\D", string.Empty);
    }
    sw.Stop();
    Console.WriteLine("RegEx took {0}ms", sw.ElapsedMilliseconds);

    Console.ReadLine();