Fields

Any useful class contains fields - variables that hold data relevant to the class.

For example, in the Person class declared in a recent article, we have two fields: name and age.

class Person
{
    public string name;
    public int age;
}

Defining a field

Inside of a class, we define a field by specifying its access modifier (like public), its data type (like string or int), and its name (like name or age).

Use this syntax on any line inside the class body:

access_modifier data_type field_name;

For example, to define a field named height of type float with private access, we would write:

public float height;

Access modifiers

An access modifier tells us who can access a field of a class.

There are a few common access modifiers in C#:

Access Modifier	Description
public	The field can be accessed from anywhere.
private	The field can only be accessed within the class.
protected	The field can be accessed within the class and by inheriting classes.
internal	The field can be accessed within the same assembly.

If there are no access modifiers on it, the field is private by default.

Example

Let’s say we created a Car class with fields for make, price, and year.

class Car
{
    public string make;
    private float price;
    public int year;
}

Because we’re a car-salesman, we want to keep the price field private so that only the Car class can access it - that way, we can charge whatever we like ;)

If we’re outside of the Car class, say, in Main, we can access the make and year fields, but not the price field:

Car myCar = new Car();
myCar.make = "Toyota"; // OK
myCar.year = 2015;     // OK
myCar.price = 6849.99; // Errors!

That’s because make and year are public, while price is private.

If however we’re in a method inside the Car class, we can access all three fields.