Variables

Variables are used to store and manipulate data. In C#, each variable has a type that determines the values it can store.

Types of variables

In C#, there are five distinct types of variables:

Syntax

type name = value;

• type: The data type of a variable, defining the kind of data it can hold.
• name: The identifier for the variable, used to reference it in the code.
• value: An optional initial value for the variable. If omitted, it must be assigned a value before use.

Examples

Local variables

In this example, localVariable can only be used within the MyMethod() function:

void MyMethod()
{
  int localVariable = 10;  // This variable is only accessible inside MyMethod
}

Instance variables

The example demonstrates an instance variable (name) within a class (Person). Each instance of Person will have its own copy of name:

class Person
{
  public string name;  // Instance variable

  public Person(string personName)
  {
    name = personName;  // Initialize instance variable
  }
}

Static Variables

Here, wheels is a static variable, meaning it belongs to the Car class and is shared by all instances. Note that static variables can be modified unless marked as const:

class Car {
  public static int wheels = 4;  // Static variable
}

Constant Variables

In this example, Pi is a constant variable, meaning its value cannot be changed after declaration and is shared across all instances:

class Circle
{
  public const double Pi = 3.14159;  // Constant variable

  public double CalculateArea(double radius)
  {
    return Pi * radius * radius;  // Using the constant variable
  }
}

Readonly Variables

In this example, length and width are readonly variables assigned in the Rectangle constructor. Their values cannot be changed after the instance is created:

class Rectangle
{
  public readonly double length;  // Readonly variable
  public readonly double width;   // Readonly variable

  public Rectangle(double l, double w)
  {
    length = l;  // Assigning value in the constructor
    width = w;   // Assigning value in the constructor
  }
}

Codebyte Example

Here’s an example showcasing the use of various types of variables:

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