C# 4.0 in a Nutshell, 4th Edition

Chapter 6. Framework Fundamentals

Many of the core facilities that you need when programming are provided not by the C# language, but by types in the .NET Framework. In this chapter, we cover the Framework’s role in fundamental programming tasks, such as virtual equality comparison, order comparison, and type conversion. We also cover the basic Framework types, such as String, DateTime, and Enum.

The types in this section reside in the System namespace, with the following exceptions:

• StringBuilder is defined in System.Text, as are the types for text encodings.

• CultureInfo and associated types are defined in System.Globalization.

• XmlConvert is defined in System.Xml.

String and Text Handling

Char

A C# char represents a single Unicode character and aliases the System.Char struct. In Chapter 2, we described how to express char literals. For example:

char c = 'A';
char newLine = '\n';

System.Char defines a range of static methods for working with characters, such as ToUpper, ToLower, and IsWhiteSpace. You can call these through either the System.Char type or its char alias:

Console.WriteLine (System.Char.ToUpper ('c'));    // C
Console.WriteLine (char.IsWhiteSpace ('\t'));     // True

ToUpper and ToLower honor the end user’s locale, which can lead to subtle bugs. The following expression evaluates to false in Turkey:

char.ToUpper ('i') == 'I'

because in Turkey, char.ToUpper ('i') is 'İ' (notice the dot on top!). To avoid this problem, System.Char (and System.String) also provides culture-invariant versions ...