In 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.
Example:
public class GFG { static public void Main () { int x; } }
Here the total number of identifers 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 “geek@” is not a valid C# identifier as it contain ‘@’ – special character.
- Identifiers should not start with digits([0-9]). For example “123geeks” is a not a valid in C# identifier.
- Identifiers should not contain white spaces.
- Identifiers are not allowed to use as keyword unless they include @ as a prefix. For example, @as is a valid identifier, but “as” is not because it is a keyword.
- C# identifers allow Unicode Characters.
- C# identifiers are case-sensitive.
- C# identifers cannot contain more than 512 characters.
- Identifiers does not contain two consecutive underscores in its name because such types of identifiers are used for the implementation.
Example:
// 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); } } |
Output:
The sum of two number is: 49
Below table shows the identifers and keywrods present in the above example:
Keywords | Identifiers |
---|---|
using | GFG |
public | Main |
static | a |
void | b |
int | c |