Constructors in C# with Example, Types of Constructor in C# with Example

Constructors in C# with Example, Types of Constructor in C# with Example

Generally constructor name should be same as class name. If we want to create constructor in a class we need to create a constructor method name same as class name check below sample method for constructor

class SampleA { public SampleA() { Console.WriteLine("Sample A Test Method"); } }

 Types of Constructors

Basically constructors are 5 types those are

      1.    Default Constructor
      2.    Parametrized Constructor
      3.    Copy Constructor
      4.    Static Constructor
      5.    Private Constructor

1.    Default Constructor

using System; namespace ConsoleApplication3 { class Sample { public string param1, param2; public Sample()     // Default Constructor { param1 = "Welcome"; param2 = "http://fantasyaspnet.blogspot.in/"; } } class Program { static void Main(string[] args) { Sample obj=new Sample();   // Once object of class created automatically constructor will be called Console.WriteLine(obj.param1); Console.WriteLine(obj.param2); Console.ReadLine(); } } }

Output:

Welcome http://fantasyaspnet.blogspot.in/

Parametrized Constructors

using System; namespace ConsoleApplication3 { class Sample { public string param1, param2; public Sample(string x, string y)     // Declaring Parameterized constructor with Parameters { param1 = x; param2 = y; } } class Program { static void Main(string[] args) { Sample obj=new Sample("Welcome","http://fantasyaspnet.blogspot.in/");   // Parameterized Constructor Called Console.WriteLine(obj.param1 +" to "+ obj.param2); Console.ReadLine(); } } }

Output:

Welcome to http://fantasyaspnet.blogspot.in/

Constructor Overloading

using System; namespace ConsoleApplication3 { class Sample { public string param1, param2; public Sample()     // Default Constructor { param1 = "Hi"; param2 = "I am Default Constructor"; } public Sample(string x, string y)     // Declaring Parameterized constructor with Parameters { param1 = x; param2 = y; } } class Program { static void Main(string[] args) { Sample obj = new Sample();   // Default Constructor will Called Sample obj1=new Sample("Welcome","http://fantasyaspnet.blogspot.in/");   // Parameterized Constructor will Called Console.WriteLine(obj.param1 + ", "+obj.param2); Console.WriteLine(obj1.param1 +" to " + obj1.param2); Console.ReadLine(); } }

Output:

Hi, I am Default Constructor Welcome to http://fantasyaspnet.blogspot.in/

Copy Constructor

using System; namespace ConsoleApplication3 { class Sample { public string param1, param2; public Sample(string x, string y) { param1 = x; param2 = y; } public Sample(Sample obj)     // Copy Constructor { param1 = obj.param1; param2 = obj.param2; } } class Program { static void Main(string[] args) { Sample obj = new Sample("Welcome", "http://fantasyaspnet.blogspot.in/");  // Create instance to class Sample Sample obj1=new Sample(obj); // Here obj details will copied to obj1 Console.WriteLine(obj1.param1 +" to " + obj1.param2); Console.ReadLine(); } } }

Output:

Welcome to http://fantasyaspnet.blogspot.in/

Static Constructor

using System; namespace ConsoleApplication3 { class Sample { public string param1, param2; static Sample() { Console.WriteLine("Static Constructor"); } public Sample() { param1 = "Sample"; param2 = "Instance Constructor"; } } class Program { static void Main(string[] args) { // Here Both Static and instance constructors are invoked for first instance Sample obj=new Sample(); Console.WriteLine(obj.param1 + " " + obj.param2); // Here only instance constructor will be invoked Sample obj1 = new Sample(); Console.WriteLine(obj1.param1 +" " + obj1.param2); Console.ReadLine(); } } }

Output:

Static Constructor Sample Instance Constructor Sample Instance Constructor

Private Constructor

using System; namespace ConsoleApplication3 { public class Sample { public string param1, param2; public Sample(string a,string b) { param1 = a; param2 = b; } private Sample()  // Private Constructor Declaration { Console.WriteLine("Private Constructor with no prameters"); } } class Program { static void Main(string[] args) { // Here we don't have chance to create instace for private constructor Sample obj = new Sample("Welcome","to http://fantasyaspnet.blogspot.in/"); Console.WriteLine(obj.param1 +" " + obj.param2); Console.ReadLine(); } } }

Output

Welcome to http://fantasyaspnet.blogspot.in/

In above method we can create object of class with parameters will work fine. If create object of class without parameters it will not allow us create.

// it will works fine Sample obj = new Sample("Welcome","to http://fantasyaspnet.blogspot.in/");  // it will not work because of inaccessability  Sample obj=new Sample();