The BCL provides rich support for text. Important types include a String class for handling immutable strings, a StringBuilder class that provides string-handling operations with support for locale-aware comparison operations and multiple string encoding formats (ASCII, Unicode, UTF-7, and UTF-8), and a set of classes that provide regular expression support (see Section 3.3 in Chapter 3).

System.Text
System.Text.RegularExpressions

Important types in other namespaces include System.String.