C# Constructors

Constructors

• A constructor is a special method called when an object is created
• It sets the initial values for fields

Constructor Syntax

• The constructor name must match the class name
• It cannot have a return type, like void or int

Creating Objects with Constructors

• When an object is created, the constructor is called
• A variable can be assigned a new object of a specific class
• The variable is a reference-type variable stored in the stack section, initially null
• Using the new keyword creates a new object in the heap
• After creating the object, the constructor is executed.
• The address of the created object is assigned to the variable using the assignment operator

Default Constructors

• All classes have constructors by default
• If a constructor is not created, C# creates one with no parameters

Constructor Parameters

• Constructors can take parameters to initialize fields
• string productName is an example of a string parameter
• float productPrice is an example of a float parameter

Parameter Usage

• Values are passed to the constructor to set the field values
• For instance, passing "Eggs" and 40 set the name and price, respectively

Accessing Object Fields

• A variable can be used to access object fields and print values

The "this" Keyword

• If a constructor parameter has the same name as a field, the parameter hides the field
• The this keyword refers to the current object
• It allows access from within the constructor, even with a local variable of the same name
• this.price refers to the field, price refers to the local variable
• The "this" keyword is optional if there is no local variable with the same name as the class member

Overloaded Constructors

• Constructors can be overloaded like other methods
• A class can have multiple constructors with different parameters
• For example, one with no parameters, one with one parameter, and one with two parameters

Usage of Overloaded Constructors

• With overloaded constructors, objects are created using any of the constructors
• Each constructor creates a different object

Constructor Initializers

• Constructor initializers allow one constructor to call another constructor
• The this keyword is used, as in this("Milk", 10)
• Constructor initializers help avoid duplicate code

How It Works

• The parameterless calls the two-parameters Product(string name, float price) constructor, using "Milk", 10
• Multiple constructors are defined and objects created with each constructor

Garbage Collection

• Local variables are temporary and created in the stack
• They are removed automatically when out of scope
• Local variables are temporary or automatic variables

Managing Memory

• Automatic variables are created in the stack
• Objects and arrays are not automatically removed from the heap
• Memory is allocated from the heap each time a new object is created
• The C++ language provides a delete operator for manual removal of an object
• C# does not provide a delete operator and uses a garbage collector instead

Garbage Collector

• Garbage collection relieves the programmer from manual memory cleanup
• The garbage collector performs a collection periodically to free memory
• It checks the heap for objects no longer in use and destroys them
• The garbage collector can be called manually using the GC class, but is not recommended

Destructors

• A destructor performs final clean-up when a class instance is removed from memory
• Destructors have the same name as the class but start with a tilde (~)
• Destructors cannot be overloaded, called, have access modifiers, or take parameters

Destructor Behavior

• The programmer has no control over when it is called
• The garbage collector calls the destructor if an object is eligible for destruction
• It reclaims the object's memory
• Destructors should be used to free resources allocated by the object, like windows, files, and network connections, before the object is destroyed