PhoneNumbers.NumberFormat.Builder.Build C# (CSharp) Method

            public NumberFormat Build()
            {
                return BuildPartial();
            }

        /**
        * Formats a phone number in the specified format using client-defined formatting rules. Note that
        * if the phone number has a country calling code of zero or an otherwise invalid country calling
        * code, we cannot work out things like whether there should be a national prefix applied, or how
        * to format extensions, so we return the national significant number with no formatting applied.
        *
        * @param number                        the phone number to be formatted
        * @param numberFormat                  the format the phone number should be formatted into
        * @param userDefinedFormats            formatting rules specified by clients
        * @return  the formatted phone number
        */
        public String FormatByPattern(PhoneNumber number, PhoneNumberFormat numberFormat,
            List<NumberFormat> userDefinedFormats)
        {
            int countryCallingCode = number.CountryCode;
            var nationalSignificantNumber = GetNationalSignificantNumber(number);
            // Note getRegionCodeForCountryCode() is used because formatting information for regions which
            // share a country calling code is contained by only one region for performance reasons. For
            // example, for NANPA regions it will be contained in the metadata for US.
            var regionCode = GetRegionCodeForCountryCode(countryCallingCode);
            if (!HasValidCountryCallingCode(countryCallingCode))
                return nationalSignificantNumber;

            PhoneMetadata metadata = GetMetadataForRegionOrCallingCode(countryCallingCode, regionCode);
            StringBuilder formattedNumber = new StringBuilder(20);
            NumberFormat formattingPattern =
                ChooseFormattingPatternForNumber(userDefinedFormats, nationalSignificantNumber);
            if (formattingPattern == null)
            {
                // If no pattern above is matched, we format the number as a whole.
                formattedNumber.Append(nationalSignificantNumber);
            }
            else
            {
                var numFormatCopy = new NumberFormat.Builder();
                // Before we do a replacement of the national prefix pattern $NP with the national prefix, we
                // need to copy the rule so that subsequent replacements for different numbers have the
                // appropriate national prefix.
                numFormatCopy.MergeFrom(formattingPattern);
                String nationalPrefixFormattingRule = formattingPattern.NationalPrefixFormattingRule;
                if (nationalPrefixFormattingRule.Length > 0)
                {
                    String nationalPrefix = metadata.NationalPrefix;
                    if (nationalPrefix.Length > 0)
                    {
                        // Replace $NP with national prefix and $FG with the first group ($1).
                        nationalPrefixFormattingRule = NP_PATTERN.Replace(nationalPrefixFormattingRule, nationalPrefix, 1);
                        nationalPrefixFormattingRule = FG_PATTERN.Replace(nationalPrefixFormattingRule, "$$1", 1);
                        numFormatCopy.SetNationalPrefixFormattingRule(nationalPrefixFormattingRule);
                    }
                    else
                    {
                        // We don't want to have a rule for how to format the national prefix if there isn't one.
                        numFormatCopy.ClearNationalPrefixFormattingRule();
                    }
                }
                formattedNumber.Append(
                    FormatNsnUsingPattern(nationalSignificantNumber, numFormatCopy.Build(), numberFormat));
            }
            MaybeAppendFormattedExtension(number, metadata, numberFormat, formattedNumber);
            PrefixNumberWithCountryCallingCode(countryCallingCode, numberFormat, formattedNumber);
            return formattedNumber.ToString();
        }