5.2 Constructors & Destructors

Let’s go over constructors and destructors in C# — essential concepts for object initialization and cleanup.

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📌 1. Constructors

A constructor is a special method that is called automatically when an object is created.

Key Points

• Name of constructor = class name

• No return type, not even void

• Can be overloaded (multiple constructors with different parameters)

• Used to initialize fields or properties

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Example: Basic Constructor

public class Person
{
    public string Name;
    public int Age;
 
    // Constructor
    public Person(string name, int age)
    {
        Name = name;
        Age = age;
    }
 
    public void Greet()
    {
        Console.WriteLine($"Hello, my name is {Name} and I am {Age} years old.");
    }
}
 
// Create object
Person person = new Person("Alice", 25);
person.Greet(); // Hello, my name is Alice and I am 25 years old.

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Example: Constructor Overloading

public class Person
{
    public string Name;
    public int Age;
 
    public Person()  // Default constructor
    {
        Name = "Unknown";
        Age = 0;
    }
 
    public Person(string name) // Constructor with 1 parameter
    {
        Name = name;
        Age = 0;
    }
 
    public Person(string name, int age) // Constructor with 2 parameters
    {
        Name = name;
        Age = age;
    }
}

• Allows creating objects in different ways

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📌 2. Destructors

A destructor is a special method that is called automatically when an object is destroyed or garbage collected.

Key Points

• Name = ~ClassName

• No parameters, no return type

• Cannot be called explicitly

• Rarely needed in C# (garbage collector handles most cleanup)

• Typically used to release unmanaged resources

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Example: Destructor

public class Person
{
    public string Name;
 
    public Person(string name)
    {
        Name = name;
        Console.WriteLine($"{Name} created");
    }
 
    // Destructor
    ~Person()
    {
        Console.WriteLine($"{Name} destroyed");
    }
}
 
// Usage
Person person = new Person("Alice");

• Destructor runs automatically when the object is garbage collected.

• In modern C#, prefer IDisposable and using statement for resource cleanup.

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📌 3. Constructor vs Destructor

Feature	Constructor	Destructor
Purpose	Initialize object	Cleanup before object is destroyed
Name	Same as class name	~ClassName
Return type	None	None
Parameters	Can have parameters	Cannot have parameters
Call	Automatically on object creation	Automatically on garbage collection
Overloading	Yes	No

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✅ Tips

• Always use constructors to set default or required values for fields.

• Avoid relying on destructors for resource cleanup — use IDisposable instead.

• C# automatically provides a default constructor if you don’t define one.