oops concept

 Object Oriented programming is a programming style that is associated with the concept of Class, Objects and various other concepts revolving around these two, like Inheritance, Polymorphism, Abstraction, Encapsulation etc.

Let us try to understand a little about all these, through a simple example. Human Beings are living forms, broadly categorized into two types, Male and Female. Right? It’s true. Every Human being (Male or Female) has two legs, two hands, two eyes, one nose, one heart etc. There are body parts that are common for Male and Female, but then there are some specific body parts, present in a Male which are not present in a Female, and some body parts present in Female but not in Males.

All Human Beings walk, eat, see, talk, hear etc. Now again, both Male and Female, performs some common functions, but there are some specifics to both, which is not valid for the other. For example: A Female can give birth, while a Male cannot, so this is only for the Female.

Human Anatomy is interesting, isn't it? But let's see how all this is related to C++ and OOPS. Here we will try to explain all the OOPS concepts through this example and later we will have the technical definitions for all this.

Class

Here we can take Human Being as a class. A class is a blueprint for any functional entity which defines its properties and its functions. Like Human Being, having body parts, and performing various actions.

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Inheritance

Considering Human Being a class, which has properties like hands, legs, eyes etc., and functions like walk, talk, eat, see etc. Male and Female are also classes, but most of the properties and functions are included in Human Being, hence they can inherit everything from class Human Being using the concept of Inheritance.

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Objects

My name is Abhishek, and I am an instance/object of class Male. When we say, Human Being, Male or Female, we just mean a kind, you, your friend, me we are the forms of these classes. We have a physical existence while a class is just a logical definition. We are the objects.

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Abstraction

Abstraction means, showcasing only the required things to the outside worked while hiding the details. Continuing our example, Human Beings can talk, walk, hear, eat, but the details are hidden from the outside world. We can take our skin as the Abstraction factor in our case, hiding the inside mechanism.

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Encapsulation

This concept is a little tricky to explain with our example. Our Legs are binded to help us walk. Our hands, help us hold things. This binding of the properties to functions is called Encapsulation.

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Polymorphism

Polymorphism is a concept, which allows us to redefine the way something works, by either changing how it is done or by changing the parts using which it is done. Both the ways have different terms for them.

If we walk using our hands, and not legs, here we will change the parts used to perform something. Hence this is called Overloading.

And if there is a defined way of walking, but I wish to walk differently, but using my legs, like everyone else. Then I can walk like I want, this will be calls as Overriding.

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OOPS Concept Definitions

Now, let us discuss some of the main features of Object Oriented Programming which you will be using in C++(technically).

1.      Objects

2.      Classes

3.      Abstraction

4.      Encapsulation

5.      Inheritance

6.      Overloading

7.      Exception Handling

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Objects

Objects are the basic unit of OOP. They are instances of class, which have data members and uses various member functions to perform tasks.

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Class

It is similar to structures in C language. Class can also be defined as user defined data type but it also contains functions in it. So, class is basically a blueprint for object. It declare & defines what data variables the object will have and what operations can be performed on the class's object.

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Abstraction

Abstraction refers to showing only the essential features of the application and hiding the details. In C++, classes provide methods to the outside world to access & use the data variables, but the variables are hidden from direct access. This can be done access specifiers.

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Encapsulation

It can also be said data binding. Encapsulation is all about binding the data variables and functions together in class.

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Inheritance

Inheritance is a way to reuse once written code again and again. The class which is inherited is called base calls & the class which inherits is called derived class. So when, a derived class inherits a base class, the derived class can use all the functions which are defined in base class, hence making code reusable.

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Polymorphism

It is a feature, which lets us create functions with same name but different arguments, which will perform differently. That is function with same name, functioning in different way. Or, it also allows us to redefine a function to provide its new definition.

When an ASP.NET page runs, the page goes through a life cycle in which it performs a series of processing steps. These include initialization, instantiating controls, restoring and maintaining state, running event handler code, and rendering. The following are the various stages or events of ASP.Net page life cycle.

PreInit

1. Check the IsPostBack property to determine whether this is the first time the page is being processed.
2. Create or re-create dynamic controls.
3. Set a master page dynamically.
4. Set the Theme property dynamically.
   
   

Note: If the request is a postback then the values of the controls have not yet been restored from the view state. If you set a control property at this stage, its value might be overwritten in the next event.

Init

1. This event fires after each control has been initialized.
2. Each control's UniqueID is set and any skin settings have been applied.
3. Use this event to read or initialize control properties.
4. The "Init" event is fired first for the bottom-most control in the hierarchy, and then fired up the hierarchy until it is fired for the page itself.
   
   

InitComplete

1. Until now the viewstate values are not yet loaded, hence you can use this event to make changes to the view state that you want to ensure are persisted after the next postback.
2. Raised by the Page object.
3. Use this event for processing tasks that require all initialization to be complete.
   
   

OnPreLoad

1. Raised after the page loads view state for itself and all controls, and after it processes postback data that is included with the Request instance.
2. Before the Page instance raises this event, it loads view state for itself and all controls, and then processes any postback data included with the Request instance.
3. Loads ViewState: ViewState data are loaded to controls.
4. Loads Postback data: Postback data are now handed to the page controls.
   
   

Load

1. The Page object calls the OnLoad method on the Page object, and then recursively does the same for each child control until the page and all controls are loaded. The Load event of individual controls occurs after the Load event of the page.
2. This is the first place in the page lifecycle that all values are restored.
3. Most code checks the value of IsPostBack to avoid unnecessarily resetting state.
4. You may also call Validate and check the value of IsValid in this method.
5. You can also create dynamic controls in this method.
6. Use the OnLoad event method to set properties in controls and establish database connections.
   
   

Control PostBack Event(s)

1. ASP.NET now calls any events on the page or its controls that caused the PostBack to occur.
2. Use these events to handle specific control events, such as a Button control's Click event or a TextBox control's TextChanged event.
3. In a postback request, if the page contains validator controls, check the IsValid property of the Page and of individual validation controls before performing any processing.
4. This is just an example of a control event. Here it is the button click event that caused the postback.
   
   

LoadComplete

1. Raised at the end of the event-handling stage.
2. Use this event for tasks that require that all other controls on the page be loaded.
   
   

OnPreRender

1. Raised after the Page object has created all controls that are required in order to render the page, including child controls of composite controls.
2. The Page object raises the PreRender event on the Page object, and then recursively does the same for each child control. The PreRender event of individual controls occurs after the PreRender event of the page.
3. The PreRender event of individual controls occurs after the PreRender event of the page.
4. Allows final changes to the page or its control.
5. This event takes place before saving ViewState, so any changes made here are saved.
6. For example: After this event, you cannot change any property of a button or change any viewstate value.
7. Each data bound control whose DataSourceID property is set calls its DataBind method.
8. Use the event to make final changes to the contents of the page or its controls.
   
   

OnSaveStateComplete

1. Raised after view state and control state have been saved for the page and for all controls.
2. Before this event occurs, ViewState has been saved for the page and for all controls.
3. Any changes to the page or controls at this point will be ignored.
4. Use this event perform tasks that require the view state to be saved, but that do not make any changes to controls.
   
   

Render Method

1. This is a method of the page object and its controls (and not an event).
2. The Render method generates the client-side HTML, Dynamic Hypertext Markup Language (DHTML), and script that are necessary to properly display a control at the browser.

UnLoad

1. This event is used for cleanup code.
2. At this point, all processing has occurred and it is safe to dispose of any remaining objects, including the Page object.
3. Cleanup can be performed on:
   
   
• Instances of classes, in other words objects
• Closing opened files
• Closing database connections.
4. This event occurs for each control and then for the page.
5. During the unload stage, the page and its controls have been rendered, so you cannot make further changes to the response stream.
6. If you attempt to call a method such as the Response.Write method then the page will throw an exception.
   
   

Web Role: Web roles in Windows Azure are special purpose, and provide a dedicated Internet Information Services (IIS) web-server used for hosting front-end web applications. You can quickly and easily deploy web applications to Web Roles and then scale your compute capabilities up or down to meet demands.

Worker Role: Worker roles are processes that can do some work. For example, automatically compress uploaded images, do stuff whenever something changes in your database, and get new messages from queues and processes.

Queue: A Queue is something that contains a set of messages and all messages must be in the queue.

Note: Web Roles, Worker Roles and Queue are actually VMs.

The definitions above may be insufficient to make your point crystal clear but that's okay, you will not work on them in this article, you just need to understand Web Role here.