Variables in C#

Last Updated : 3 Oct, 2026

Variables in C# are named storage locations used to store data that can be accessed and manipulated during program execution. Each variable is declared with a specific data type and name and can optionally be initialized with a value.

  • Data Type: Specifies the type of data a variable can store, such as int, double, or string.
  • Variable Name: Identifies the variable and must follow C# identifier rules.
  • Value (Optional): Can be assigned during declaration or later in the program.
C# 
using System;

class Geeks
{
    static void Main()
    {
        // Declaring and initializing variables

        // Integer variable
        int age = 25;

        // String variable
        string name = "GeeksforGeeks";

        // Double variable
        double salary = 50000.50;

        // Displaying the values of variables
        Console.WriteLine("Age: " + age);
        Console.WriteLine("Name: " + name);
        Console.WriteLine("Salary: " + salary);
    }
}

Output

Age: 25
Name: GeeksforGeeks
Salary: 50000.5

Declaration

A variable declaration in C# specifies the data type and variable name.

Datatypes Variable_Name;

variable1

A variable declaration consists of two main components: the data type and the variable name.

Here, int is the data type and count is the variable name.

Initialization

Initialization means assigning an initial value to a variable.

A variable can be declared and initialized at the same time.

int age; // Declaration
age = 25; // Assignment
int marks = 90; // Declaration + initialization

variable2

Here:

  • int is the data type.
  • age is the variable name.
  • 25 is the value assigned to age.

Example of Variable Initialization

Here is an example of initializing variables of different types such as float, int, and char.

C# 
using System;

class Geeks
{
    static void Main()
    {
        // Declaring and initializing variables

        // Initializing float variable
        float si = 5.5f;

        // Initializing integer variables
        int t = 10;
        int s = 20;

        // Initializing character variable
        char var = 'h';

        // Displaying the values of the variables
        Console.WriteLine("Simple Interest: " + si);
        Console.WriteLine("Speed: " + s);
        Console.WriteLine("Time: " + t);
        Console.WriteLine("Character: " + var);
    }
}

Output:

Simple Interest: 5.5
Speed: 20
Time: 10
Character: h

Naming Rules of C# Variables

C# has certain rules that must be followed when naming variables.

1. Valid Characters

Variable names can contain letters, digits, and underscores (_). C# also supports Unicode characters in identifiers.

Valid examples:

int age;
int studentAge;
int total_marks;

2. Starting Character

A variable name cannot start with a digit. It generally starts with a letter or underscore.

Valid:

int age;
int _count;

Invalid:

int 2age;

3. No Reserved Keywords

C# reserved keywords such as int, class, and if cannot normally be used as variable names.

For example:

int int; // Invalid

If necessary, C# provides the @ prefix for using a keyword as an identifier:

int @class = 10;

However, using meaningful non-keyword names is generally preferred.

4. Case-Sensitive

C# is case-sensitive. Therefore, age, Age, and AGE are considered different identifiers.

int age = 20;
int Age = 30;

These are two different variables.

5. No Spaces

Variable names cannot contain spaces.

Invalid:

int student age;

Use camelCase instead:

int studentAge;

6. Use Meaningful Names

Variable names should clearly indicate what the variable stores.

Instead of:

int s = 90;

prefer:

int studentMarks = 90;

Meaningful names make the code easier to read and understand.

7. Naming Convention

For local variables and parameters, C# commonly uses camelCase.

Examples:

int studentAge;
double totalSalary;
string studentName;

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