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 D

Answer 1

public static string DigitsOnly(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
            });
}