There was a time when people thought of computers as manipulating numeric values exclusively. Among the first uses of computers was to calculate missile trajectories during World War II, and for a very long time programming was taught in the math department of major universities.
Today, most programs are concerned more with manipulating and displaying strings of characters in addition to strings of numbers. Typically, these strings are used for word processing, document manipulation, and the creation of web pages.
C# provides built-in support for a fully functional string type. More importantly, C# treats strings as objects that encapsulate all the manipulation, sorting, and searching methods normally applied to strings of characters.
Tip
The .NET Framework provides a String class (uppercase S). The C# language offers an alias to the String class as the string class (lowercase s). These class names are interchangeable, and you are free to use either upper- or lowercase.
Complex string manipulation and pattern matching is aided by the use of regular expressions. Regular expressions are a powerful technology for describing and manipulating text. Underlying regular expressions is a technique called pattern matching, which involves comparing one string to another, or comparing a series of wildcards that represent a type of string to a literal string. A regular expression is applied to a string—that is, to a set of characters. Often, that string is an entire text document. We’ll explain regular expressions in more detail later in this chapter.
In this chapter, you will learn to work with the C# string type and the .NET Framework System.String class that it aliases. You will see how to extract substrings, manipulate and concatenate strings, and build new strings with the StringBuilder class. In addition, you will find a short introduction to the Regex class used to match strings based on regular expressions.