Lesson 11 — OOP Foundations

Classes and Objects

C# classes and objects work like Java's with additional ergonomics: object initialiser syntax, primary constructors (C# 12), and records for immutable data.

CSHARP — Learner class 
public class Learner {
    public string Name;
    public int    Age;
    public string Course;

    public void Introduce() =>
        Console.WriteLine($"I am {Name}, aged {Age}, studying {Course} at Your IT Tutor.");

    public string GradeLabel() => Mark switch {
        >= 80 => "Distinction",
        >= 60 => "Merit",
        >= 50 => "Pass",
        _     => "Not yet competent"
    };

    public double Mark { get; set; } // auto-property
}

Object Initialiser Syntax

C# lets you set public properties and fields inline at construction — no need for a matching constructor overload.

CSHARP — Object initialiser 
// Standard construction then assignment:
var l1 = new Learner();
l1.Name   = "Thandi";
l1.Age    = 21;
l1.Course = "C#";
l1.Mark   = 74.5;

// Object initialiser — same result, much cleaner:
var l2 = new Learner { Name = "Sipho", Age = 24, Course = "Java", Mark = 81.0 };

l1.Introduce();
l2.Introduce();
Console.WriteLine(l2.GradeLabel()); // Merit

Records — Immutable Data Classes

Records are a concise way to define immutable data types. The compiler generates constructor, properties, equality, ToString, and deconstruct automatically.

CSHARP — Records 
// One line replaces 30 lines of boilerplate:
record Learner(string Name, int Age, string Course, double Mark);

var l1 = new Learner("Thandi", 21, "C#", 74.5);
var l2 = new Learner("Thandi", 21, "C#", 74.5);

Console.WriteLine(l1);          // Learner { Name = Thandi, ... }
Console.WriteLine(l1 == l2);    // True — records compare by value

// with expression — create a modified copy:
var l3 = l1 with { Mark = 82.0 };
Console.WriteLine(l3);

Practice Task

Your Turn

Create a Product class with Name, Price (decimal), Category (string), InStock (bool). Use object initialiser to create 3 products. Create a ProductRecord record with the same fields. Create one record instance and show that value equality works (two records with identical data are equal).

Common Mistakes

  • Public fields are fine here but real code uses Properties (Lesson 12).
  • Forgetting new.
  • C# method names are PascalCase.
  • Records are immutable — use with to create modified copies.

Professional Tip

Use records for data transfer objects, value objects, and configuration — anything that is fundamentally 'data with no behaviour'. Use regular classes when the object has mutable state and behaviour.

Mini Quiz

What does C# object initialiser syntax allow?