C# | Identifiers

In C# | Identifiers programming languages, identifiers are used for identification purposes. Or in other words, identifiers are the user-defined name of the program components. In C#, an identifier can be a class name, method name, variable name, or label. 


public class GFG {
    static public void Main () 
          int x;

Here the total number of identifiers present in the above example is 3 and the names of these identifiers are: 

  • GFG: Name of the class
  • Main: Method name
  • x: Variable name

Rules for defining identifiers in C#:

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

  • The only allowed characters for identifiers are all alphanumeric characters([A-Z][a-z][0-9]), ‘_‘ (underscore). For example “tech@” is not a valid C# identifier as it contain ‘@’ – special character.
  • Identifiers should not start with digits([0-9]). For example “123tech” is not valid in the C# identifier.
  • Identifiers should not contain white spaces.
  • 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.
  • C# identifiers allow Unicode Characters.
  • C# identifiers are case-sensitive.
  • C# identifiers cannot contain more than 512 characters.
  • Identifiers do not contain two consecutive underscores in their name because such types of identifiers are used for the implementation.


// Simple C# program to illustrate identifiers
using System;
class GFG {
    // Main Method
    static public void Main()
        // variable
        int a = 10;
        int b = 39;
        int c;
        // simple addition
        c = a + b;
        Console.WriteLine("The sum of two number is: {0}", c);


The sum of two number is: 49

Below table shows the identifiers and keywords present in the above example: