What are the Characteristics of the Object-Oriented Approach?

Following are the characteristics of the Object-Oriented Approach:

• Realistic Modeling

       

The Object-Oriented approach allows you to identify entities as objects having attributes and behavior. Attributes and behavior typically dipct how the object acts and reacts. For example, the car is an object belonging to the class Vehicle. The car has attributes such as speed, color, and power. It displays behavior such as being stationary, moving slowly, or accelerating.

• Reusability

          In programming word, using existing classes or objects form other application saves resources spent in recreating the classes from scratch. The process of creating a new class by adding some features to an existing class is known as inheritance. The benefit of reputability translates to savings in time and effort, which in turn results in cost benefits.

• Resilience to Change

          In the object-oriented system, this requirement does not mean that the new car needs to be built from scratch. The new features can be easily incorporated in the old system without modifying the base attributes.

          Resilience to change also results in easier maintenance. This feature of object-oriented methodology is known as extensibility. The ability of a class to inherit features from another class also makes object-oriented programs more extensible. For the same reason, even during construction, parts of the system under development can be refined without any major changes to other parts.

• Existence as Different Forms

          Using the object-oriented approach, objects can be made to respond differently to the same message. the response is decided based on the information or parameters provided with the message. This ability to react differently based on the information associated with the message is known as polymorphisum.

What are the new features of C# 6.0?

C# 6.0 is the latest version which ships with Visual Studio 2015. You to start learning the new features to update yourselves for many different reasons. C# 6.0 is not yet completed and Microsoft is releasing few features now and then. For interview point of view, just mentioned the following items and you should be satisfying the interviewer question.

Following are few features of C# 6.0

1. $ sign

The purpose for it is to simplify string based indexing. Its not some thing like current dynamic features of  C# since it internally uses regular indexing functionality. To understand lets consider following example:

  var col = new Dictionary()
            {
                // using inside the intializer
                $first = "Hassan"
            };

   //Assign value to member

   //the old way:
   col["first"] = "Hassan";
 
   // the new way
   col.$first = "Hassan";

2. Exception filters:

Exception filters are already supported in VB compiler but now they are coming into C#. exception filters lets you specify a condition for a catch block. the catch block gets executed only if the condition is satisfied, this one is my favorite feature, so let's look at an example:

            try
            {
                throw new Exception("Me");
            }
            catch (Exception ex) if (ex.Message == "You")
            {
                // this one will not execute.
            }
            catch (Exception ex) if (ex.Message == "Me")
            {
                // this one will execute
            }

3. await in catch and finally block:

As far as I know, no one know why in C# 5 using await keyword in catch and finally block was not available, any way its now possible to use though. this is great because often we want to perform I/O operation in order to log the exception reason in catch block or such things in finally block and they Need asynchrony.

            try
            {
                DoSomething();
            }
            catch (Exception)
            {
                await LogService.LogAsync(ex);
            }

4. Declaration expressions

This feature simply allows you to declare local variable in the middle of an expression. It is as simple as that but really destroys a pain. I have been doing a lot of asp.net web form projects in the past and this was my every day code:

long id;
if (!long.TryParse(Request.QureyString["Id"], out id))
{ }
which can be improved to this:
Hide   Copy Code
if (!long.TryParse(Request.QureyString["Id"], out long id))
{ }

The scoping rules for this kind of declaration is same as general scoping rules in C#.

5. using Static

This feature allows you to specify a particular type in a using statement after that all static members of that type will be accessible is subsequent code.

using System.Console;

namespace ConsoleApplication10
{
    class Program
    {
        static void Main(string[] args)
        {
            //Use writeLine method of Console class
            //Without specifying the class name
            WriteLine("Hellow World");
        }
    }
}

6. Auto property initializer:

With C# 6 initialize auto properties just like a field at declaration place. The only thing to notice here is that this initialization dose not cause the setter function to be invoked internally. the value of backing field is set directly. so here is an example:

public class Person
    {
        // You can use this feature on both
        //getter only and setter / getter only properties

        public string FirstName { get; set; } = "Hassan";
        public string LastName { get; } = "Hashemi";
    }

7. Primary Constructor:

The main purpose for it is using constructor parameters for initialization. When declaring a primary constructor all other constructors must call the primary constructor using :this().
here is an example finally:

    //this is the primary constructor:
    class Person(string firstName, string lastName)
    {
        public string FirstName { get; set; } = firstName;
        public string LastName  { get; } = lastName;
    }

notice that declaration of primary constructor is at the top of the class.

8- Dictionary Initializer:

Some people believed that the old way of initiailzing dictionaries was dirty so the C# team dicided to make it cleaner, thanks to them. here is an example of the old way and new way:


            // the old way of initializing a dictionary
            Dictionary oldWay = new Dictionary()
            {
                { "Afghanistan", "Kabul" },
                { "United States", "Washington" },
                { "Some Country", "Some Capital city" }
            };

            // new way of initializing a dictionary
            Dictionary newWay = new Dictionary()
            {
                // Look at this!
                ["Afghanistan"] = "Kabul",
                ["Iran"] = "Tehran",
                ["India"] = "Delhi"
            };

Note: To play around and know more about C# 6.0 download Visual Studio 2015 click here

What is a Class in Object Oriented Programming (OOP)?

Definition:

Class is a declaration, a template, or a blueprint that can be used to classify objects.

For example, the peacock, the sparrow, and the kingfisher are all birds. All of them share characteristics that are common to the family of birds. All of them lay eggs, are covered with feathers, have hollow bone structures, and have the ability to fly. Therefore, they share structural and behavioral similarities and belong to the class called Birds.

What is an object in Object Orientation (OOP)?

Definition 1:

An object is a combination of messages and data. Objects can receive and send messages and use messages to interact with each other. The messages contain information that is to be passed to the recipient object.


Definition 2:

An object literally means a 'material thing' that is capable of being presented to the senses.


Definition 3:

An object is a tangible entity that may exhibit some well-defined behavior. For example, let us consider a tennis ball:

• A tennis ball is a tangible entity, with a visible boundary.
• A tennis ball has a specific defined purpose (such as bouncing)
• You can direct a specific action towards a tennis ball by hitting it with racquet or by tossing it.