Use of Constructor and Destructor ?

Question

Hello For what purpose we are using constructor and destructor in a Program.....[Constructor Overloading] We wanna use this mandatory...! Please clarify me....

Muralidharan Deenathayalan · Answer

//Constructors are used to create a object for a class. public class Person { public string Name { get ; set ;} public int Id{ get ; set ;} //Default constructor or silent constructor public Person () { Console. WriteLine ( Default constructor called ); } public Person ( string Name) { this .Name = Name; Console. WriteLine ( One arguemented constructor called ); Console. WriteLine ( Person name is  + this .Name); } public Person ( string Name int Id) { this .Name = Name; this .Id = Id; Console. WriteLine ( Two arguemented constructor called ); Console. WriteLine ( Person name is  + this .Name +  id  + this .Id); } public virtual void draw () { Console. WriteLine ( Base class draw method called ); } ~ Person () { Console. WriteLine ( Destructor called ); } } public class Employee : Person { public override void draw () { Console. WriteLine ( Child class draw method called ); } } Person p = new Person (); p. draw (); Employee emp = new Employee (); emp. draw (); The person object will call the draw method from person and Employee object method will call the draw method from employee class. To override the method in child class in the base class that method should be marked as virtual then you can override it in the child class. If the method is not marked as virtual in the base class still can override it by using new keyword instead of override. public new void draw () { Console. WriteLine ( Child class draw method called ); }

Muralidharan Deenathayalan · Answer

//Constructors are used to create a object for a class. public class Person { public string Name { get ; set ;} public int Id{ get ; set ;} //Default constructor or silent constructor public Person () { Console. WriteLine ( Default constructor called ); } public Person ( string Name) { this .Name = Name; Console. WriteLine ( One arguemented constructor called ); Console. WriteLine ( Person name is  + this .Name); } public Person ( string Name int Id) { this .Name = Name; this .Id = Id; Console. WriteLine ( Two arguemented constructor called ); Console. WriteLine ( Person name is  + this .Name +  id  + this .Id); } ~ Person () { Console. WriteLine ( Destructor called ); } } //You can creat object for person in multiple ways Person person = new Person (); //Which calls default constructor person = new Person ( Murali ); //Which calls single argumented constructor person = new Person ( Murali  10 ); //Which calls two argumented constructor //Destructors are used to dispose an object.To call the destructor call GC.Collect(); System.GC. Collect ();

Vulpes · Answer

In Murali's example where he has in the Employee class: public new void draw() try removing 'new' and then study the compiler output when you rebuild. Similarly add this method to the Employee class and look at the compiler output: public new void draw2() { }

Vijay · Answer

Vulpes plz mention some examples what u said  'new' to hide an inherited member is never necessary. However if you don't use it when it should be used then the compiler will issue a warning. Similarly if you use it when it shouldn't be used then the compiler will warn you about that as well.

Vulpes · Answer

Notice that the use of 'new' to hide an inherited member is never necessary. However if you don't use it when it should be used then the compiler will issue a warning. Similarly if you use it when it shouldn't be used then the compiler will warn you about that as well. However because you can't both hide and override an inherited member at the same time the combination 'new override' is not allowed and gives a compiler error.

Vijay · Answer

thank u very much Muralidharan Deenathayalan and Iftikar Hussain .....

Muralidharan Deenathayalan · Answer

//Constructors are used to create a object for a class. public class Person { public string Name { get ; set ;} public int Id{ get ; set ;} //Default constructor or silent constructor public Person () { Console. WriteLine ( Default constructor called ); } public Person ( string Name) { this .Name = Name; Console. WriteLine ( One arguemented constructor called ); Console. WriteLine ( Person name is  + this .Name); } public Person ( string Name int Id) { this .Name = Name; this .Id = Id; Console. WriteLine ( Two arguemented constructor called ); Console. WriteLine ( Person name is  + this .Name +  id  + this .Id); } public void draw () { Console. WriteLine ( Base class draw method called ); } ~ Person () { Console. WriteLine ( Destructor called ); } } public class Employee : Person { public new void draw () { Console. WriteLine ( Child class draw method called ); } } Person p = new Person (); p. draw (); Employee emp = new Employee (); emp. draw (); The derived class method is preceded with the new keyword the method is defined as being independent of the method in the base class. The override modifier extends the base class method and the new modifier hides it. To know more about on the new and override keyword http://msdn.microsoft.com/en-us/library/ms173153.aspx

Vijay · Answer

what is use of new keyword and where we can use this ? Is it access modifier ? give samples sir...... public new void draw () { }

Vijay · Answer

Thanks Muralidharan Deenathayalan ... I get clear about this.... Give example for method loading and overriding using class

Muralidharan Deenathayalan · Answer

You can't override constructor because the constructors will not be inherited to the child class. You can override base class methods in the child class but not the constructors.

Muralidharan Deenathayalan · Answer

Constructor overloading example Person person = new Person (); //Which calls default constructor person = new Person ( Murali ); //Which calls single parameterized constructor person = new Person ( Murali  10 ); //Which calls two parameterized constructor

Vijay · Answer

thanks Iftikar Hussain and Muralidharan Deenathayalan H ow can use method overriding and loading using constructor... plz give example

Iftikar Hussain · Answer

Hi Please refer the below link In Constructor http://www.dotnetspider.com/forum/171656-constructor-uses-Purpose.aspx In Destructor http://www.c-sharpcorner.com/UploadFile/chandrahundigam/UnderstandingDestructors11192005021208AM/UnderstandingDestructors.aspx Regards Iftikar