Extract numbers from string to create digit only string [duplicate]

Answer 1

Here's the version that worked for my case

    public static string ExtractNumbers(this string source)
    {
        if (String.IsNullOrWhiteSpace(source))
            return string.Empty;
        var number = Regex.Match(source, @"\d+");
        if (number != null)
            return number.Value;
        else
            return string.Empty;
    }