Classes

A reference type that encapsulates behavior.

Characteristics

Allocation: Heap
Equality: Reference
Semantics: Reference (a variable of a class contains a reference to that class)
Inheritance: Single
Mutability: Mutable

Use When

You need to describe behavior and not just data

Creating Classes

Note: When creating custom classes, always override ToString() to provide information about the type (not shown here).

public class Point
{
    private int _X { get; } // Auto-implemented readonly property.
    private int _Y { get; }

    // Constructor that takes 0 arguments:
    public Point() => (0, 0);

    // Constructor that takes 2 arguments:
    public Point(int x, int y) => (_X, _Y) = (x, y);
    // This constructor also ensures that _X and _Y are set so that they cannot be null, avoiding null reference.

    // Another example that uses the "this" keyword to refer to members of the instance:
    public Point(int x, int y) 
    {
        this._X = x;
        this._Y = y;
    }

    // A method that overrides the base class (System.Object) implementation of ToString():
    public override string ToString() => return $"({X}, {Y})"
}

Creating Objects (Instantiating a Class)

var p = new Point(x: *n*, y: *m*) // Constructor syntax.
p = new Point { x = *n*, y = *m* } // Initializer syntax.
Point p = new() { x = n, y = m }

Equality

Object.Equals Boolean if two reference-type objects refer to the same location in memory.