A read only field is declared with readonly modifier.
A read only field cannot change its value after declaration or outside the constructors.
using System;
class Rectangle{
public readonly int Width = 3;
public readonly int Height = 4;
}
class Program
{
static void Main(string[] args)
{
Rectangle r = new Rectangle();
Console.WriteLine(r.Width);
}
}
The output:
3
The code above initialize the readonly fields when declaring them.
We can also set the value in the contructor.
using System;
class Rectangle {
public readonly int Width;
public readonly int Height;
public Rectangle(){
Width = 5;
}
}
class Program
{
static void Main(string[] args)
{
Rectangle r = new Rectangle();
Console.WriteLine(r.Width);
}
}
The output:
5