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Capitalization Conventions

The guidelines in this chapter lay out a simple method for using case that, when applied consistently, make identifiers for types, members, and parameters easy to read.

To differentiate words in an identifier, capitalize the first letter of each word in the identifier. Do not use underscores to differentiate words, or for that matter, anywhere in identifiers. There are two appropriate ways to capitalize identifiers, depending on the use of the identifier:

  • PascalCasing

  • camelCasing

The PascalCasing convention, used for all identifiers except parameter names, capitalizes the first character of each word (including acronyms over two letters in length), as shown in the following examples:

PropertyDescriptor
HtmlTag

A special case is made for two-letter acronyms in which both letters are capitalized, as shown in the following identifier:

IOStream

The camelCasing convention, used only for parameter names, capitalizes the first character of each word except the first word, as shown in the following examples. As the example also shows, two-letter acronyms that begin a camel-cased identifier are both lowercase.

propertyDescriptor
ioStream
htmlTag

√ DO use PascalCasing for all public member, type, and namespace names consisting of multiple words.

√ DO use camelCasing for parameter names.

The following table describes the capitalization rules for different types of identifiers.

Identifier

Casing

Example

Namespace

Pascal

namespace System.Security { ... }

Type

Pascal

public class StreamReader { ... }

Interface

Pascal

public interface IEnumerable { ... }

Method

Pascal

public class Object {
public virtual string ToString();
}

Property

Pascal

public class String {
public int Length { get; }
}

Event

Pascal

public class Process {
public event EventHandler Exited;
}

Field

Pascal

public class MessageQueue {
public static readonly TimeSpan
InfiniteTimeout;
}
public struct UInt32 {
public const Min = 0;
}

Enum value

Pascal

public enum FileMode {
Append,
...
}

Parameter

Camel

public class Convert {
public static int ToInt32(string value);
}

Most compound terms are treated as single words for purposes of capitalization.

X DO NOT capitalize each word in so-called closed-form compound words.

These are compound words written as a single word, such as endpoint. For the purpose of casing guidelines, treat a closed-form compound word as a single word. Use a current dictionary to determine if a compound word is written in closed form.

Pascal

Camel

Not

BitFlag

bitFlag

Bitflag

Callback

callback

CallBack

Canceled

canceled

Cancelled

DoNot

doNot

Don't

Email

email

EMail

Endpoint

endpoint

EndPoint

FileName

fileName

Filename

Gridline

gridline

GridLine

Hashtable

hashtable

HashTable

Id

id

ID

Indexes

indexes

Indices

LogOff

logOff

LogOut

LogOn

logOn

LogIn

Metadata

metadata

MetaData, metaData

Multipanel

multipanel

MultiPanel

Multiview

multiview

MultiView

Namespace

namespace

NameSpace

Ok

ok

OK

Pi

pi

PI

Placeholder

placeholder

PlaceHolder

SignIn

signIn

SignOn

SignOut

signOut

SignOff

UserName

userName

Username

WhiteSpace

whiteSpace

Whitespace

Writable

writable

Writeable

Languages that can run on the CLR are not required to support case-sensitivity, although some do. Even if your language supports it, other languages that might access your framework do not. Any APIs that are externally accessible, therefore, cannot rely on case alone to distinguish between two names in the same context.

X DO NOT assume that all programming languages are case sensitive. They are not. Names cannot differ by case alone.

Portions © 2005, 2009 Microsoft Corporation. All rights reserved.

Reprinted by permission of Pearson Education, Inc. from Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries, 2nd Edition by Krzysztof Cwalina and Brad Abrams, published Oct 22, 2008 by Addison-Wesley Professional as part of the Microsoft Windows Development Series.

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