---
title: PhoneNumberFormatter
summary: API reference for PhoneNumberFormatter.
status: draft
owner: SAIF Doc Gen
last_reviewed: 2026-09-24
library: SAIF.Services
reference_type: package
---

# PhoneNumberFormatter

Formats a phone number (with an optional extension) into SAIF's preferred display style (`###.###.####` with an optional ` x<extension>` suffix), delegating the digit validation and splitting work to an internally constructed `PhoneNumberParser`.

## Purpose
- Produces the SAIF-preferred, dot-separated display format for a phone number, appending an extension when supplied.
- Falls back to the original, unformatted input when the number cannot be parsed as a standard 10-digit US number.

## Context
- Namespace: `SAIF.Services.Utilities`
- Assembly/package: `SAIF.Services` (packaged inside the `SAIF.SAIFCode.Core` NuGet package)

## Public members
| Member | Signature | Purpose |
| --- | --- | --- |
| PhoneNumberFormatter(phoneNumber) | `public PhoneNumberFormatter(string phoneNumber)` | Stores the raw phone number to format, with no extension. |
| PhoneNumberFormatter(phoneNumber, extension) | `public PhoneNumberFormatter(string phoneNumber, string extension)` | Stores the raw phone number and an extension to append when formatting. |
| SaifPreferredDisplayPhoneNumber | `public string SaifPreferredDisplayPhoneNumber { get; }` | The phone number formatted as `AAA.PPP.NNNN`, with ` x<extension>` appended when an extension was supplied and the number parses successfully; otherwise the original input string unchanged. |

## Behavioral notes
- Formatting logic is entirely re-evaluated on each access of `SaifPreferredDisplayPhoneNumber` (it is a computed property, not a cached value)*.

> **Note:** Statements marked with * were inferred from code structure, naming conventions, or
> contextual evidence where direct confirmation was not available in source artifacts. Statements
> marked with ** could not be confirmed; treat as unknown until verified.

## Sources
- Services/SAIF.Services/Utilities/PhoneNumberFormatter.cs