Destructor in C#

Destructor is a special method that get invoked / called automatically whenever an object of a given class gets destroyed. Main idea behind using destructor is to free the memory used by the object.

Constructor in C#

Constructor is a special method that get invoked / called automatically whenever an object of a given class gets instantiated.

Interfaces in C#

An interface is similar to a class with method signatures. There wont be any implementation of the methods in Interface. Classes which implements interface should have implementation of methods defined in abstract class

Sealed Classes in c#

If a class is defined as Sealed it cannot be inherited in derived class.

public sealed class Car
{

public Car()
{
Console.WriteLine("Base Class Car");
}

public void DriveType()
{
Console.WriteLine("Right Hand ");
}
} 

Abstract Class in C#

If we don't want a class object to be created define the class as abstract. An abstract class can have abstract and non abstract classes. If a method in abstract id defined as abstract , it must be implemented in derived class. For example , in the classes given below , method DriveType is defined as abstract. 

abstract class Car
{
public Car()
{
Console.WriteLine("Base Class Car");
}
public abstract void DriveType();
}

class Ford : Car
{
public void DriveType()
{
Console.WriteLine("Right Hand ");
}
}

Method Hiding in C#

If the derived class doesn't want to use methods in base class , derived class can implement the same method in derived class with same signature. For example in the classes given below, DriveType() is implemented in the derived class with same signature. This is called Method Hiding.

class Car
{
public void DriveType()
{
Console.WriteLine("Right Hand Drive");
}
}

class Ford : Car
{
public void DriveType()
{
Console.WriteLine("Right Hand ");
}
}

Javascript How to get unique values in a array

var a = ["1", "1", "2", "3", "3", "1"];
var unique = a.filter(function(item, i, ar){ return ar.indexOf(item) === i; });