Field and Property.md

Field & Property

Fields and Properties are a member of a class/interface/struct. They are used to define attributes of a class/interface/struct they belong into.

Although both field and properties can be used to do the same job, properties are the 99.99% go-to for attributes.

Field & Property syntax

Field

class Person
{
    public int Age;
}

Property

class Person
{
    private int age;
    public int Age
    {
        get
        {
            return age;
        }
        set
        {
            age = value;
        }
    }
}

In properties, there are two new keywords you'll encounter, get and set. In this example, when you assign something to Age, the code within set is executed. And when you call Age, the code within get is executed.

Both of the above do the same thing, to provide the age of a person object.

Usage of fields and properties

Let's say that I have a class called Circle and it has attributes named Radius, Diameter and Circumference.

Since diameter and circumference can be computed directly from radius itself, the best way to go along with this would be to implement 3 public properties that would expose a private radius field.

class Circle
{
    private double radius;
    
    public double Radius
    {
        get => radius;
        set => radius = value;
    }
    public double Diameter
    {
        get
        {
            return radius * 2;
        }
    }
    public double Circumference
    {
        get
        {
            return radius * 2 * Math.PI;
        }
    }
}

With this, you only need to write at Radius and then the change would immediately reflect at Diameter and Circumference.

Do note that in properties, when you don't define a get, you won't be able to call the value of that property, making it a write-only property. Respectively, by omitting the set, it'll become a read-only property.

By using a private field, you can use properties as a way to expose the values of those private fields and gives you the ability to perform validations through the property itself. This way, the information that should contain within that class, will remain within that class through the use of fields and properties.