Chapter 2. Strings and Characters

String usage abounds in just about all types of applications. The System.String type does not derive from System.ValueType and is therefore considered a reference type. The string alias is built into C# and can be used instead of the full name.

The FCL does not stop with just the string class; there is also a System.Text.StringBuilder class for performing string manipulations and the System.Text.RegularExpressions namespace for searching strings. This chapter will cover the string class and the System.Text.StringBuilder class.

The System.Text.StringBuilder class provides an easy, performance friendly, method of manipulating string objects. This class duplicates much of the functionality of a string class. However, this duplicated functionality provides a more efficient manipulation of strings than is obtainable by using the string class.

2.1. Determining the Kind of Character

Problem

You have a variable of type char and wish to determine the kind of character it contains—a letter, digit, number, punctuation character, control character, separator character, symbol, whitespace, or surrogate character. Similarly, you have a string variable and want to determine the kind of character in one or more positions within this string.

Solution

Use the built-in static methods on the System.Char structure shown here:

Char.IsControl
Char.IsDigit
Char.IsLetter
Char.IsNumber
Char.IsPunctuation
Char.IsSeparator
Char.IsSurrogate
Char.IsSymbol
Char.IsWhitespace ...

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