Choose variable names that follow rules and conventions
- 6 minutes
A software developer once famously said, "The hardest part of software development is naming things." Not only does the name of a variable have to follow certain syntax rules, it should also be used to make the code more human-readable and understandable. That's a lot to ask of one line of code!
Variable name rules
There are some variable naming rules that are enforced by the C# compiler.
- Variable names can contain alphanumeric characters and the underscore (_) character. Special characters like the pound
#, the dash-, and the dollar sign$are not allowed. - Variable names must begin with an alphabetical letter or an underscore, not a number. Using an underscore character to start a variable name is typically reserved for private instance fields. A link to further reading can be found in the module summary.
- Variable names must NOT be a C# keyword. For example, these variable name declarations won't be allowed:
float float;orstring string;. - Variable names are case-sensitive, meaning that
string MyValue;andstring myValue;are two different variables.
Variable name conventions
Conventions are suggestions that are agreed upon by the software development community. While you're free to decide not to follow these conventions, they're so popular that it might make it difficult for other developers to understand your code. You should practice adopting these conventions and make them part of your own coding habits.
- Variable names should use camel case, which is a style of writing that uses a lower-case letter at the beginning of the first word and an upper-case letter at the beginning of each subsequent word. For example:
string thisIsCamelCase;. - Variable names should be descriptive and meaningful in your application. You should choose a name for your variable that represents the kind of data it will hold (not the data type). For example:
bool orderComplete;, NOTbool isComplete;. - Variable names should be one or more entire words appended together. Don't use contractions because the name of the variable may be unclear to others who are reading your code. For example:
decimal orderAmount;, NOTdecimal odrAmt;. - Variable names shouldn't include the data type of the variable. You might see some advice to use a style like
string strMyValue;. It was a popular style years ago. However, most developers don't follow this advice anymore and there are good reasons not to use it.
The example string firstName; follows all of these rules and conventions, assuming you want to use this variable to store data that represents someone's first name.
Variable name examples
Here's a few examples of variable declarations (using common data types):
char userOption;
int gameScore;
float particlesPerMillion;
bool processedCustomer;
Other naming conventions
The rules and conventions described above are for local variables. A local variable is a variable that is scoped within the body of a method, or a variable in a console application that uses top-level statements (like the code in this module).
There are other types of constructs that you can use in your applications, and many have their own conventions. For example, classes are often used in C# programming, and have associated conventions. Although you won't be creating classes in this module, it's important for you to know that the naming conventions you just learned about fit into a larger naming framework.