#18 – What Is an Identifier?

An identifier is any name that you choose to use in a C# program for things like: variables, classes, interfaces, methods, properties, etc.

The rules for naming identifiers include:

• They are case sensitive  (i.e. “name” is different from “Name”)
• They must begin with a letter or underscore (‘_’)
• They cannot include spaces
• They can include Unicode characters
• They cannot match any of the built-in C# keywords

You can actually name an identifier with a name matching a built-in keyword if you prefix the identifer with the ‘@’ symbol.  In the following example, we declare a variable of type string and name the variable “string”.  This is legal in C#, but not a good practice.

string @string = "Don't do this";