Encapsulation

Encapsulation is defined 'as the process of enclosing one or more items within a physical or logical package'. Encapsulation, in object oriented programming methodology, prevents access to implementation details.
Abstraction and encapsulation are related features in object oriented programming. Abstraction allows making relevant information visible and encapsulation enables a programmer to implement the desired level of abstraction.

What is Encapsulation?

What is Abstraction?

What is the functionality of Encapsulation and Abstraction in C#?

Encapsulation and abstraction is essential part of C sharp programming that is mostly used for hide complex code from unauthorized user and shows only relevant information.

What is encapsulation?

Encapsulation is the process of hiding irrelevant data from the user. To understand encapsulation, consider an example of mobile phone. Whenever youbuy a mobile, you don’t see how circuit board works. You are also not interested to know how digital signal converts into analog signal and vice versa. These are the irrelevant information for the mobile user, that’s why it is encapsulated inside a cabinet.

In C# programming, we will do same thing. We will create a cabinet and keep all the irrelevant information in it that will be unavailable for the user.

What is abstraction?

Abstraction is just opposite of Encapsulation. Abstraction is mechanism to show only relevant data to the user. Consider the same mobile example again. Whenever you buy a mobile phone, you see their different types of functionalities as camera, mp3 player, calling function, recording function, multimedia etc. It is abstraction, because you are seeing only relevant information instead of their internal engineering.

Encapsulation is implemented by using access specifiers. An access specifier defines the scope and visibility of a class member. C# supports the following access specifiers:

• Public
• Private
• Protected
• Internal
• Protected internal

Public Access Specifier

Public access specifier allows a class to expose its member variables and member functions to other functions and objects. Any public member can be accessed from outside the class.The type or member can be accessed by any other code in the same assembly or another assembly that references it.
The following example illustrates this:

using System;
namespace RectangleApplication
{
    class Rectangle
    {
        //member variables
        public double length;
        public double width;

        public double GetArea()
        {
            return length * width;
        }
        public void Display()
        {
            Console.WriteLine("Length: {0}", length);
            Console.WriteLine("Width: {0}", width);
            Console.WriteLine("Area: {0}", GetArea());
        }
    }//end class Rectangle    
    class ExecuteRectangle
    {
        static void Main(string[] args)
        {
            Rectangle r = new Rectangle();
            r.length = 4.5;
   r.width = 3.5;
            r.Display();
            Console.ReadLine();
        }
    }
}

When the above code is compiled and executed, it produces following result:

Length: 4.5
Width: 3.5
Area: 15.75

In the preceding example, the member variables length and width are declared public, so they can be accessed from the function Main() using an instance of the Rectangle class, named r.
The member function Display() and GetArea() can also access these variables directly without using any instance of the class.
The member functions Display() is also declared public, so it can also be accessed from Main() using an instance of the Rectangle class, named r.

Private Access Specifier

Private access specifier allows a class to hide its member variables and member functions from other functions and objects. Only functions of the same class can access its private members. Even an instance of a class cannot access its private members.
The following example illustrates this:

using System;
namespace RectangleApplication
{
    class Rectangle
    {
        //member variables
        private double length;
        private double width;

        public void Acceptdetails()
        {
            Console.WriteLine("Enter Length: ");
            length = Convert.ToDouble(Console.ReadLine());
            Console.WriteLine("Enter Width: ");
            width = Convert.ToDouble(Console.ReadLine());
        }
        public double GetArea()
        {
            return length * width;
        }
        public void Display()
        {
            Console.WriteLine("Length: {0}", length);
            Console.WriteLine("Width: {0}", width);
            Console.WriteLine("Area: {0}", GetArea());
        }
    }//end class Rectangle    
    class ExecuteRectangle
    {
        static void Main(string[] args)
        {
            Rectangle r = new Rectangle();
            r.Acceptdetails();
            r.Display();
            Console.ReadLine();
        }
    }
}

When the above code is compiled and executed, it produces following result:

Enter Length:
4.4
Enter Width:
3.3
Length: 4.4
Width: 3.3
Area: 14.52

In the preceding example, the member variables length and width are declared private, so they cannot be accessed from the function Main(). The member functions AcceptDetails() and Display() can access these variables. Since the member functions AcceptDetails() and Display() are declared public, they can be accessed from Main() using an instance of the Rectangle class, named r.

Protected Access Specifier

Protected access specifier allows a child class to access the member variables and member functions of its base class. This way it helps in implementing inheritance. We will discuss this in more details in the inheritance chapter.

Example:


using System;

namespace Protected_Specifier
{
  class access
   {
     // String Variable declared as protected
     protected string name;
     public void print()
      {
        Console.WriteLine("\nMy name is " + name);
      }
   }

  class Program
   {
     static void Main(string[] args)
      {
        access ac = new access();
        Console.Write("Enter your name:\t");
        // raise error because of its protection level
        ac.name = Console.ReadLine();
        ac.print();
        Console.ReadLine();
      }
   }
}



Output:
'Protected_Specifier.access.name' is inaccessible due to its protection level.

This is because; the protected member can only be accessed within its child class. You can use protected access specifiers as follow:

Example:


using System;

namespace Protected_Specifier
{
  class access
   {
     // String Variable declared as protected
     protected string name;
     public void print()
      {
        Console.WriteLine("\nMy name is " + name);
      }
   }

  class Program : access // Inherit access class
   {
     static void Main(string[] args)
      {
        Program p=new Program();
        Console.Write("Enter your name:\t");
        p.name = Console.ReadLine(); // No Error!!
        p.print();
        Console.ReadLine();
      }
   }
}

Internal Access Specifier

Internal access specifier allows a class to expose its member variables and member functions to other functions and objects in the current assembly. In other words, any member with internal access specifier can be accessed from any class or method defined within the application in which the member is defined.

The type or member can be accessed by any code in the same assembly, but not from another assembly.
Whereas assembly is a project which is compiled together.
The following program illustrates this:

using System;
namespace RectangleApplication
{
    class Rectangle
    {
        //member variables
        internal double length;
        internal double width;
        
        double GetArea()
        {
            return length * width;
        }
       public void Display()
        {
            Console.WriteLine("Length: {0}", length);
            Console.WriteLine("Width: {0}", width);
            Console.WriteLine("Area: {0}", GetArea());
        }
    }//end class Rectangle    
    class ExecuteRectangle
    {
        static void Main(string[] args)
        {
            Rectangle r = new Rectangle();
            r.length = 4.5;
            r.width = 3.5;
            r.Display();
            Console.ReadLine();
        }
    }
}

When the above code is compiled and executed, it produces following result:

Length: 4.5
Width: 3.5
Area: 15.75

In the preceding example, notice that the member function GetArea() is not declared with any access specifier. Then what would be the default access specifier of a class member if we don't mention any? It is private.

Output 

Enter your name:     Steven Clark

My name is Steven Clark 

Protected Internal Access Specifier

The protected internal access specifier allows a class to hide its member variables and member functions from other class objects and functions, except a child class within the same application. This is also used while implementing inheritance.

Example:

using System;

namespace Internal_Access_Specifier
{
  class access
   {
     // String Variable declared as internal
     internal string name;
     public void print()
      {
        Console.WriteLine("\nMy name is " + name);
      }
   }

  class Program
   {
     static void Main(string[] args)
      {
        access ac = new access();
        Console.Write("Enter your name:\t");
        // Accepting value in internal variable
        ac.name = Console.ReadLine();
        ac.print();
        Console.ReadLine();
      }
   }
}

Output 

Enter your name:     Steven Clark

My name is Steven Clark