Different ways to create an Object in C#

18 Aug, 2021
A fully object-oriented language means everything is represented as an object but can’t differentiate between primitive types and objects of classes but C# is not purely object oriented since it supports many procedural programming concepts such as pointers to an extent. An object is a basic unit of Object Oriented Programming and represents the real-life entities. A typical C# program creates many objects, which as you know, interact by invoking methods. We can Create objects in C# in the following ways:1) Using the ‘new’ operator: A class is a reference type and at the run time, any object of the reference type is assigned a null value unless it is declared using the new operator. The new operator assigns space in the memory to the object only during run time which means the allocation is dynamic.Syntax:  
// The className() is a call
// to the constructor
className ObjectName = new className();   
Note: The constructor can be a default constructor or a user-defined one.Example: 
csharp
// C# Program to show the use// of the new Operatorusing System; namespace NewOperator { class Rectangle {     public int length, breadth;     // Parameterized Constructor    // User defined    public Rectangle(int l, int b)    {        length = l;        breadth = b;    }     // Method to Calculate Area    // of the rectangle    public int Area()    {        return length * breadth;    }} // Driver Classclass Program {     // Main Method    static void Main(string[] args)    {        // Creating an object using 'new'        // Calling the parameterized constructor        // With parameters 10 and 12        Rectangle rect1 = new Rectangle(10, 12);         // To display are of the Rectangle        int area = rect1.Area();        Console.WriteLine("The area of the"+                   " Rectangle is " + area);    }}}
The area of the Rectangle is 120
 
2) Creating Reference to Existing Object: The reference can be declared only with the class name and reference name. The reference cannot exist independently. It has to be assigned to an already existing object of the same class. Any changes made in the reference will be saved to the object it is referring to. It is kind of like an alias.Syntax:  
className RefName;
RefName = objectName;
Example: 
csharp
// C# Program to show the use// of referencesusing System; namespace Reference { class Triangle {     public int side, altitude;    // Not defining a constructor     // Method to calculate area    // of the Triangle    public double Area()    {        return (double)0.5 * side * altitude;    }} // Driver Classclass Program {     // Main Method    static void Main(string[] args)    {        // Creating an object using new        // calls the default constructor        Triangle tri1 = new Triangle();         // Only creates a reference of        // type Triangle        Triangle tri2;         // Displaying area of tri1        Console.WriteLine("Area of tri1 is "                             + tri1.Area());         // Assigns the reference to tri1        tri2 = tri1;         // Making changes in tri2        tri2.side = 5;        tri2.altitude = 7;         // Displaying area of tri1        // Changes made in the reference tri2        // are reflected in tri1 also        Console.WriteLine("Area of tri1 is "                             + tri1.Area());    }}}
Area of tri1 is 0
Area of tri1 is 17.5
 
3) Creating an Array of objects: If you need the multiple numbers of objects of the same class you can create an array of objects. This will require you to declare the array first and then initialize each element { object in this case }. You can use for loop for initialization.Syntax:  
className[] arrayName = new className[size];
 
csharp
// C# Program to illustrate how to// create the array of objectsusing System; namespace ArrayofObjects { class Circle {     public int radius;     // Defining Constructor    public Circle()    {        radius = 0;    }     // Method to set value of radius    public void setValue(int r)    {        radius = r;    }     // Method to calculate the    // area of the Circle    public double Area()    {        return (double)3.14 * radius * radius;    }} // Driver Classclass Program {     // Main Method    static void Main(string[] args)    {        // To declare an array of two objects        Circle[] circleArray = new Circle[2];         // Initialize the objects        circleArray[0] = new Circle();        circleArray[1] = new Circle();         // to set values for the radius        circleArray[0].setValue(1);        circleArray[1].setValue(2);         // for loop to display areas        for (int i = 0; i < circleArray.Length; i++)        {            Console.Write("Area of circle with radius " + (i + 1));            Console.Write(" is " + circleArray[i].Area() + "\n");        }    }}}
Area of circle with radius 1 is 3.14
Area of circle with radius 2 is 12.56
 
adnanirshad158
CSharp-OOP
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C#
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