Parameterized constructor

C# course · Intermediate · Lesson 8/116

Learn to initialize objects with parameterized constructors.

Parameterized constructor

Constructors can take parameters. This way you can pass initial values from outside when creating the object: public Car(string make) { Make = make; }.

The call also has parameters: new Car("Toyota"). Here "Toyota" is passed to the constructor as make and assigned to the Make property. A parameterized constructor puts the object into a valid state the moment it is created; no separate assignment lines are needed.

Multiple parameters

A constructor can take multiple parameters separated by commas: public Car(string make, string model, int year). The call gives values in the same order: new Car("Toyota", "Corolla", 2020).

Order matters: the first value goes to make, the second to model, the third to year. Wrong order sends wrong values. In constructors with many parameters, meaningful names prevent confusion.

Exercise Add a parameterized constructor to Car

Add public string Make { get; set; }, public string Model { get; set; } and public int Year { get; set; } properties to the Car class. Then declare a three-parameter constructor that assigns each parameter to its property. Inside Main create an instance with new Car("Toyota", "Corolla", 2020) and print Make.

Show example solution

Define three properties and a three-parameter constructor. In Main write Car c = new Car("Toyota", "Corolla", 2020); Console.WriteLine(c.Make);
Example solution:
using System;

class Car
{
    public string Make { get; set; }
    public string Model { get; set; }
    public int Year { get; set; }

    public Car(string make, string model, int year)
    {
        Make = make;
        Model = model;
        Year = year;
    }
}

class Program
{
    static void Main()
    {
        Car c = new Car("Toyota", "Corolla", 2020);
        Console.WriteLine(c.Make);
    }
}

Test yourself

Complete the parameter declaration

public Car(string ____) { Make = make; }

Show answer

public Car(string make) { Make = make; }

Which is a parameterized constructor call?
```
public Car(string make, string model, int year) { ... }
```
- new Car("Toyota", "Corolla", 2020)
- new Car()
- new Car[]
- Car()
Show answer

new Car("Toyota", "Corolla", 2020) — Correct. Three arguments map to three parameters in order.
Match each parameter to its type

string make

Text
int year

Whole number
decimal price

Decimal number
bool active

True/false

Parameterized constructor