21.2 Reading a Quick-Reference Entry

Each quick-reference entry contains quite a bit of information. The sections that follow describe the structure of a quick-reference entry, explaining what information is available, where it is found, and what it means. While reading the descriptions that follow, you will find it helpful to flip through the reference section itself to find examples of the features being described.

21.2.1 Type Name, Namespace, Assembly, Type Category, and Flags

Each quick-reference entry begins with a four-part title that specifies the name, namespace (followed by the assembly in parentheses), and type category of the type. It may also specify various additional flags that describe the type. The type name appears in bold at the upper left of the title. The namespace and assembly appear, in smaller print, in the lower left, below the type name.

In the upper-right corner of the title, you may find a list of flags that describe the type. The possible flags and their meanings are as follows:

ECMA: The type is part of the ECMA CLI specification.
Serializable: The type, or a supertype, implements System.Runtime.Serialization.ISerializable or has been flagged with the System.Serializable attribute.
Marshal by reference: This class, or a superclass, derives from System.MarshalByRefObject.
Context bound: This class, or a superclass, derives from System.ContextBoundObject.
Disposable: The type implements the System.IDisposable interface.
Flag: The enumeration is marked with the System.FlagsAttribute.

The lower-right portion of the title indicates the type category of the type (class, delegate, enum, interface, or struct). The class category may include modifiers, such as sealed or abstract.

21.2.2 Description

The title of each quick-reference entry is followed by a short description of the most important features of the type. This description may be anywhere from a couple of sentences to several paragraphs long.

21.2.3 Synopsis

The most important part of every quick-reference entry is the synopsis, which follows the title and description. The synopsis for a type looks a lot like its source code, except that the member bodies are omitted, and some additional annotations are added. If you know C# syntax, you can read the type synopsis.

The first line of the synopsis contains information about the type itself. It begins with a list of type modifiers, such as abstract and sealed. These modifiers are followed by the class, delegate, enum, interface, or struct keyword, and then by the name of the type. The type name may be followed by a colon (:) and a supertype or interfaces that the type implements.

The type-definition line is followed by a list of the members that the type defines. This list includes only those members that are explicitly declared in the type, are overridden from a base class, or are implementations of an interface member. Members that are simply inherited from a base class aren't shown; you will need to look up the base class definition to find those members. Once again, if you understand basic C# syntax, you should have no trouble making sense of these lines. The listing for each member includes the modifiers, type, and name of the member. For methods, the synopsis also includes the type and name of each method parameter. The member names are in boldface, so it is easy to scan the list of members looking for the one you want. The names of method parameters are in italics to indicate that they aren't to be used literally. The member listings are printed on alternating gray and white backgrounds to keep them visually separate.

21.2.3.1 Member availability and flags

Each member listing is a single line that defines the API for that member. These listings use C# syntax, so their meaning is immediately clear to any C# programmer. There is some auxiliary information associated with each member synopsis, however, that requires explanation.

The area to the right of the member synopsis displays a variety of flags that provide additional information about the member. Some of these flags indicate additional specification details that don't appear in the member API itself.

The following flags may be displayed to the right of a member synopsis:

Overrides: Indicates that a method overrides a method in one of its supertypes. The flag is followed by the name of the supertype that the method overrides.
Implements: Indicates that a method implements a method in an interface. The flag is followed by the name of the interface that is implemented.
=: For enumeration fields and constant fields, this flag is followed by the constant value of the field. Only constants of primitive and String types and constants with the value null are displayed. Some constant values are specification details, while others are implementation details. The reason symbolic constants are defined, however, is so you can write code that doesn't directly rely on the constant value. Use this flag to help you understand the type, but don't rely on the constant values in your own programs.

21.2.3.2 Functional grouping of members

Within a type synopsis, the members aren't listed in strict alphabetical order. Instead, they are broken into functional groups and listed alphabetically within each group. Constructors, events, fields, methods, and properties are all listed separately. Instance methods are kept separate from static (class) methods. Public members are listed separately from protected members. Grouping members by category breaks a type down into smaller, more comprehensible segments, making the type easier to understand. This grouping also makes it easier for you to find a desired member.

Functional groups are separated from one another in a type synopsis with C# comments, such as // Public Constructors, // Protected Instance Properties, and // Events. The various functional categories are as follows (in the order in which they appear in a type synopsis):

Constructors: Displays the constructors for the type. Public constructors and protected constructors are displayed separately in subgroupings. If a type defines no constructor at all, the C# compiler adds a default no-argument constructor that is displayed here. If a type defines only private constructors, it can't be instantiated, so no constructor appears. Constructors are listed first, because the first thing you do with most types is instantiate them by calling a constructor.
Fields: Displays all fields defined by the type, including constants. Public and protected fields are displayed in separate subgroups. Fields are listed here, near the top of the synopsis, because constant values are often used throughout the type as legal values for method parameters and return values.
Properties: Lists all the properties of the type, breaking them down into subgroups for public and protected static properties and public and protected instance properties. After the property name, its accessors (get or set) are shown.
Static Methods: Lists the static methods (class methods) of the type, broken into subgroups for public static methods and protected static methods.
Public Instance Methods: Contains all public instance methods.
Protected Instance Methods: Contains all protected instance methods.

21.2.4 Class Hierarchy

For any type that has a nontrivial inheritance hierarchy, the synopsis is followed by a Hierarchy section. This section lists all the supertypes of the type, as well as any interfaces implemented by those supertypes. It also lists any interfaces implemented by an interface. In the hierarchy listing, arrows indicate supertype-to-subtype relationships, while the interfaces implemented by a type follow the type name in parentheses. For example, the following hierarchy indicates that SomeClass implements IDisposable and extends MarshalByRefObject, which itself extends Object:

System.Object  System.MarshalByRefObject  SomeClass(System.IDisposable)

If a type has subtypes, the Hierarchy section is followed by a Subtypes section that lists those subtypes. If an interface has implementations, the Hierarchy section is followed by an Implementations section that lists those implementations. While the Hierarchy section shows ancestors of the type, the Subtypes or Implementations section shows descendants.

21.2.5 Cross-References

The Hierarchy section of a quick-reference entry is followed by a number of optional cross-reference sections that indicate related types and methods that may be of interest. These sections are the following:

Passed To: This section lists all the members (from other types) that are passed an object of this type as an argument, including properties whose values can be set to this type. This is useful when you have an object of a given type and want to know where it can be used.
Returned By: This section lists all the members that return an object of this type, including properties whose values can take on this type. This is useful when you want to work with an object of this type but don't know how to obtain one.
Valid On: For attributes, this lists the attribute targets the attribute can be applied to.
Associated Events: For delegates, this lists the events it can handle.

21.2.6 A Note About Type Names

Throughout the quick reference, you'll notice that types are sometimes referred to by type name alone and at other times referred to by type name and namespace. If namespaces were always used, the type synopses would become long and hard to read. On the other hand, if namespaces were never used, it would sometimes be difficult to know what type was being referred to. The rules for including or omitting the namespace name are complex. They can be summarized approximately however, as follows:

If the type name alone is ambiguous, the namespace name is always used.
If the type is part of the System namespace or is a commonly used type such as System.Collection.ICollection, the namespace is omitted.
If the type being referred to is part of the current namespace (and has a quick-reference entry in the current chapter), the namespace is omitted. The namespace is also omitted if the type being referred to is part of a namespace that contains the current namespace.

[ Team LiB ]