C# in a Nutshell, Second Edition

XML Documentation

C# offers three different styles of source-code documentation: single-line comments, multiline comments, and documentation comments.

C/C++-Style Comments

Single- and multiline comments use the C++ syntax, // and /*...*/:

int x = 3; // this is a comment
MyMethod( ); /* this is a
comment that spans two lines */

The disadvantage of this style of commenting is that there is no predetermined standard for documenting types. Consequently, it cannot be easily parsed to automate the production of documentation. C# improves on this by allowing you to embed documentation comments in the source, and by providing an automated mechanism for extracting and validating documentation at compile time.

Documentation Comments

Documentation comments are composed of embedded XML tags. These tags allow one to mark up the descriptive text to better define the semantics of the type or member, and also to incorporate cross-references. Documentation comments must either start with /// (that’s three slashes), or (as of Visual C# 2003) be contained in multiline comments (that’s /* ... */). They can be applied to any user-defined type or member.

These comments can then be extracted at compile time into a separate output file containing the documentation. The compiler validates the comments for internal consistency, expands cross-references into fully qualified type IDs, and outputs a well-formed XML file. Further processing is left up to you, although a common next step is to run the XML through ...