How to set property via setter

Question

I have been taught in school about C#. We did some basic stuff like loops, if etc.

Now we do more about OOP. Teacher said us something about auto-implemented-property and I find this feature as great. But I am curious how can I set value of property via method.

When we didn't know auto-implemented-property. We always did a method to set or get value of class. But when I use auto-implemented-property I do not see any methods to get or set value of class instance. So how can I set the value of some property of class when I can set the value only via constructor. I want to know that, because when property is private I can set it only via constructor, which is not a problem, but what I can do when I want to set value via Console.Readline(); ?

namespace _001_dedicnost
{    
    class Car
    {        
        int Size { get; set; }                              
    }
    class Program
    {
        static void Main(string[] args)
        {
            Car car1 = new Car(5);
            // but the following line wont work
            car1.Set(51);
        }
    }
}

Answer 1

Your class Car have PRIVATE property Size, so u cant't have access to it from your code, only from class CAR

If u want to set value to this property, u have to declare it PUBLIC:

 class Car
        {
            public int Size { get; set; }
        }

        static void Main(string[] args)
        {
            Car car1 = new Car();
            car1.Size = 1;
        }

Answer 2

When you put the property on the left-hand side of an expression, the set method is automatically called on it with the right-hand side of the expression as the value.

So car1.Size = 51 is like calling the expanded setter for the Size property with value being 51.

Answer 3

This

public class Point {
    public int X { get; set; } = 0;
}

is equivalent to the following declaration:

public class Point {
    private int __x = 0;
    public int X { get { return __x; } set { __x = value; } }
}

This means you have "couple of 'methods' under c sharp compilator which called using '=' sign"

Point p = new Point();
p.X = 10; //c# compiler would call something like p.__set_X(10)
int i = p.X; //c# compiler would call something like int i = p.__get_X();

Read more about auto-properties https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/language-specification/classes#automatically-implemented-properties

Btw I dont recommend to use it - it breaks readability and refactobility of code ;(

Answer 4

If the class is a simple anemic model (without logic), set the property as public , and it will work.

If you want to control the invariants (business rules), you'd want to have a public Size { get; private set; } public Size { get; private set; } public Size { get; private set; } with a public void SetSize(int size) { /* ... */ } which contains your business rules.

Here are three 'patterns' normally used in C#:

// Anemic domain model (simple entity)
public class Car
{
    public int Size { get; set;}
}

// Domain model with business rules
public class Car
{
    public int Size { get; private set; }

    public void SetSize (int size)
    {
        // check to make sure size is within constraints
        if (size < 0 || size > 100)
            throw new ArgumentException(nameof(size));

        Size = size;
    }
}

// Value object
public class Car
{
    public Car (int size) 
    {
        // check constraints of size
        Size = size;
    }
    public int Size { get; }
}