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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