Monday, November 1, 2021

C# Constructor and its types


Constructor and Its Types

What Is a Constructor?

C# is an object-oriented programming (OOP) language where the object is the fundamental programming unit. When an object is created, a template, known as a class, is used in OOP.

A class consists of two main parts:

  1. Fields: These represent the data of the object.
  2. Methods: These operate on the class's data and outline its behavior.

To create an object of a class, the new operator is used. The constructor of the class is invoked by the new keyword during object creation. A constructor initializes the fields of the class associated with the object. Initialization involves assigning initial values to the fields of the class.

What Is a Constructor in Detail?

A constructor is a special method used to initialize the fields of a class. Its primary purpose is to assign initial values to fields, enabling the creation of objects. A constructor:

  • Does not return any value, as its purpose is solely to initialize fields.
  • Conventionally has the same name as the class.
  • Is always defined inside the class it belongs to.
  • Has a scope defined using access modifiers like public, private, or protected (with the exception of static constructors).

Every class must have a constructor, either explicitly defined by the programmer or implicitly provided by the compiler.


Types of Constructors

Implicit Constructor (Default Constructor)

An implicit constructor is automatically provided by the compiler when no constructor is explicitly defined in the class. It initializes all fields of the class to their default values based on their data type:

  • int: Default value is 0.
  • string: Default value is null.
  • bool: Default value is false.

Features of Default Constructor:

  • It is always public and parameterless.
  • It is not visible in the class (implicit).
  • It is executed by the compiler when an object is created using the new operator.
  • It is not available when the programmer defines any constructor explicitly.

Explicit Constructor

An explicit constructor is defined by the programmer. It can either:

  • Be parameterless.
  • Take parameters to initialize fields with specific values.

Key Features:

  • Allows initialization of fields with different values for different objects.
  • Can have any access modifier (public, private, protected, etc.).
  • Enables creating different instances of a class with varied initial values.

Private Constructor

A private constructor restricts object creation to within the class itself. It is commonly used in singleton design patterns.

Protected Constructor

A protected constructor allows object creation only within the class or its derived classes.

Parameterized Constructor

A parameterized constructor allows the programmer to pass specific values to initialize the fields of a class.

  • If incorrect data types are passed as arguments, the object creation fails.

Static Constructor

A static constructor initializes the static fields of a class and:

  1. Is implicitly called by the runtime, not explicitly by the programmer.
  2. Executes only once during the lifecycle of the class.
  3. Is parameterless and cannot be overloaded.
  4. Runs before any instance or non-static members are accessed.

Differences Between Static and Non-Static Constructors:

  1. A class has a static constructor only if it contains static fields.
  2. A static constructor is implicitly called, while a non-static constructor is explicitly called by the programmer.
  3. A static constructor is executed once during the class's lifecycle, whereas a non-static constructor can be invoked multiple times.
  4. A static constructor cannot have access modifiers or parameters, whereas a non-static constructor can.

Copy Constructor

A copy constructor is a non-static, parameterized constructor that takes an object of the same class as its parameter. It creates a new object by copying data from an existing object.


Conclusion

Constructors play a crucial role in object-oriented programming by initializing class fields during object creation. Whether implicit or explicit, constructors ensure that every object is initialized properly. Different types of constructors offer flexibility in designing classes and managing object behavior.

 

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