ทำความเข้าใจคุณสมบัติและเมธอด

using System;

class Person {
    private int age;

    public int Age {
        get { return age; }
        set {
            if (value > 0) {
                age = value; // Only assign valid ages
            } else {
                Console.WriteLine("Age must be positive.");
            }
        }
    }
}

class Program {
    static void Main() {
        Person person = new Person();
        person.Age = 25; // Valid value
        Console.WriteLine("Age: " + person.Age);

        person.Age = -5; // Invalid value
    }
}

using System;

class Car {
    public string Model { get; set; }
    public string Color { get; set; }
}

class Program {
    static void Main() {
        Car car = new Car { Model = "Sedan", Color = "Blue" };
        Console.WriteLine("Model: " + car.Model + ", Color: " + car.Color);
    }
}

using System;

class Calculator {
    public int Add(int a, int b) {
        return a + b; // Adds two numbers
    }
}

class Program {
    static void Main() {
        Calculator calc = new Calculator();
        int result = calc.Add(10, 5); // Call the method
        Console.WriteLine("Sum: " + result);
    }
}

using System;

class Greeter {
    public void Greet(string name) {
        Console.WriteLine("Hello, " + name + "!");
    }
}

class Program {
    static void Main() {
        Greeter greeter = new Greeter();
        greeter.Greet("Alice");
        greeter.Greet("Bob");
    }
}

using System;

class Rectangle {
    public int Length { get; set; }
    public int Width { get; set; }

    public int CalculateArea() {
        return Length * Width;
    }
}

class Program {
    static void Main() {
        Rectangle rect = new Rectangle { Length = 5, Width = 4 };
        Console.WriteLine("Area: " + rect.CalculateArea());
    }
}