---
title: StringUtilities
summary: API reference for StringUtilities.
status: draft
owner: saif-docgen
last_reviewed: 2026-09-15
library: SAIF.Framework.Common
reference_type: package
---

# StringUtilities

Static character-class filters that extract or strip specific categories of characters (digits, letters, punctuation, symbols, control characters, whitespace) from a string. ([BR-075](<../../business-rules.md#br-075-character-class-filters-retain-(or%2C-for-the-remove-variants%2C-exclude)-exactly-the-characters-matching-the-corresponding-char.is-predicate%2C-and-treat-a-null-input-as-an-empty-string>))

## Purpose
- Static character-class filters that extract or strip specific categories of characters (digits, letters, punctuation, symbols, control characters, whitespace) from a string. ([BR-075](<../../business-rules.md#br-075-character-class-filters-retain-(or%2C-for-the-remove-variants%2C-exclude)-exactly-the-characters-matching-the-corresponding-char.is-predicate%2C-and-treat-a-null-input-as-an-empty-string>))

## Context
- Namespace: `SAIF.Common.Utility`
- Assembly/package: `SAIF.Framework.Common`

## Public members
| Member | Signature | Purpose |
| --- | --- | --- |
| Digits(this string value) | `public static string Digits(this string value)` | Returns only the characters for which `char.IsDigit` is true. |
| Letters(this string value) | `public static string Letters(this string value)` | Returns only the characters for which `char.IsLetter` is true. |
| LettersOrDigits(this string value) | `public static string LettersOrDigits(this string value)` | Returns only the characters for which `char.IsLetterOrDigit` is true. |
| Punctuation(this string value) | `public static string Punctuation(this string value)` | Returns only the characters for which `char.IsPunctuation` is true. |
| Symbols(this string value) | `public static string Symbols(this string value)` | Returns only the characters for which `char.IsSymbol` is true. |
| ControlCharacters(this string value) | `public static string ControlCharacters(this string value)` | Returns only the characters for which `char.IsControl` is true. |
| RemoveControlCharacters(this string value) | `public static string RemoveControlCharacters(this string value)` | Returns the string with every control character removed. |
| RemoveWhiteSpaces(this string value) | `public static string RemoveWhiteSpaces(this string value)` | Returns the string with every whitespace character removed. |


## Sources
- `Common/SAIF.Common/Utility/StringUtilities.cs`