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C# Identifiers

Last Updated : 28 Apr, 2026

In C#, identifiers are the user-defined names given to program elements such as variables, methods, classes, and labels. They are used to identify these elements in a program. Example: 

In the above code block- "x", "GFG" and "Main" are identifiers representing a variable, class, and method, respectively and are user-defined names used to uniquely identify program elements in C#.

Rules for Defining Identifiers

There are certain valid rules for defining a valid C# identifier. These rules should be followed, otherwise, we will get a compile-time error.  

Aspect

Description

Allowed Characters

The only allowed characters for identifiers are all alphanumeric characters([A-Z], [a-z], [0-9]), '_' (underscore).
For example, "geek@" is not a valid C# identifier as it contains the '@' special character.

Starting Character

Identifiers should not start with digits([0-9]). For example, "123geeks" is not valid in the C# identifier.

No Whitespaces

Identifiers must not contain whitespace characters.

Keywords

Identifiers are not allowed to use as keywords unless they include @ as a prefix. For example, @as is a valid identifier, but "as" is not because it is a keyword.

Unicode Support

C# identifiers allow Unicode Characters.

Case - Sensitivity

C# identifiers are case-sensitive.

Length Restriction

There is no strict length limit defined for identifiers in C#, but they should be kept short and meaningful for readability.

Underscore Usage

Identifiers can contain underscores, but using consecutive underscores (e.g., __name) is discouraged as such patterns are typically reserved for internal or compiler-generated use.

Types of Identifiers

Identifiers in C# can represent different program elements:

  • Class Identifiers: Names of classes (e.g., GFG)
  • Method Identifiers: Names of methods (e.g., Main)
  • Variable Identifiers: Names of variables (e.g., x)
  • Object Identifiers: Names of objects created from classes

Output
The sum of two numbers is: 49

In the above example:

  • Keywords: using, public, static, void, int.
  • Identifiers: Geeks, Main , a, b, c.

Naming Conventions for Identifiers

Use meaningful names (e.g., totalMarks instead of tm). Use the following naming conventions:

  • PascalCase: for classes and methods (StudentData)
  • camelCase: for variables (studentAge)

Avoid using reserved keywords as identifiers.

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