There is a convention, and it specifies initial uppercase, the rest lowercase, for all acronyms that are more than 2 characters long. Hence HttpContext and ClientID.
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 capitalize both characters of two-character acronyms, except the
first word of a camel-cased identifier.
A property named DBRate is an example of a short acronym (DB) used as
the first word of a Pascal-cased identifier. A parameter named
ioChannel is an example of a short acronym (IO) used as the first word
of a camel-cased identifier.
Do capitalize only the first character of acronyms with three or more
characters, except the first word of a camel-cased identifier.
A class named XmlWriter is an example of a long acronym used as the
first word of a Pascal-cased identifier. A parameter named htmlReader
is an example of a long acronym used as the first word of a
camel-cased identifier.
Do not capitalize any of the characters of any acronyms, whatever
their length, at the beginning of a camel-cased identifier.
A parameter named xmlStream is an example of a long acronym (xml) used
as the first word of a camel-cased identifier. A parameter named
dbServerName is an example of a short acronym (db) used as the first
word of a camel-cased identifier.