What is ASP.Net?

ASP.Net is a web development platform, which provides a programming model, a comprehensive software infrastructure and various services required to build up robust web application for PC, as well as mobile devices.
ASP.Net works on top of the HTTP protocol and uses the HTTP commands and policies to set a browser-to-server two-way communication and cooperation.
ASP.Net is a part of Microsoft .Net platform. ASP.Net applications are complied codes, written using the extensible and reusable components or objects present in .Net framework. These codes can use the entire hierarchy of classes in .Net framework.
The ASP.Net application codes could be written in either of the following languages:

• C#
• Visual Basic .Net
• Jscript
• J#

ASP.Net is used to produce interactive, data-driven web applications over the internet. It consists of a large number of controls like text boxes, buttons and labels for assembling, configuring and manipulating code to create HTML pages.

ASP.Net Web Forms Model:

ASP.Net web forms extend the event-driven model of interaction to the web applications. The browser submits a web form to the web server and the server returns a full markup page or HTML page in response.
All client side user activities are forwarded to the server for stateful processing. The server processes the output of the client actions and triggers the reactions.
Now, HTTP is a stateless protocol. ASP.Net framework helps in storing the information regarding the state of the application, which consists of:

• Page state
• Session state

The page state is the state of the client, i.e., the content of various input fields in the web form. The session state is the collective obtained from various pages the user visited and worked with, i.e., the overall session state. To clear the concept, let us take up an example of a shopping cart as follows.
User adds items to a shopping cart. Items are selected from a page, say the items page, and the total collected items and price are shown in a different page, say the cart page. Only HTTP cannot keep track of all the information coming from various pages. ASP.Net session state and server side infrastructure keeps track of the information collected globally over a session.
The ASP.Net runtime carries the page state to and from the server across page requests while generating the ASP.Net runtime codes and incorporates the state of the server side components in hidden fields.
This way the server becomes aware of the overall application state and operates in a two-tiered connected way.

About AutoPostBack

Autopostback is the mechanism, by which the page will be posted ,back to the server automatically based on some events in the web controls. In some of the web controls, the property called auto post back, which if set to true, will send the request to the server when an event happens in the control. If this property is set to TRUE the automatic post back is enabled, otherwise FALSE. Default value of AutoPostBack property is FALSE.

For Example


Why we need to set autopostback=true of controls
Consider a scenario where the web page is used for entering the user information. The page contains two dropdownlist controls ddlcountry and ddlstate. When user selects the country, the appropriate states be filled in the ddlstate which is loaded from the database. For achieving this requirement, we can set the autopostback property of ddlcountry to true. If we do that we can handle the event in the server side and write code to populate the ddlstate with the values from the database.
This is how we use the autopostback property.

By default the button,linkbutton and imagebutton has an autopostback as an event. The code behind that you write is to handle this postback. A button cannot have an explicit button postback but is in-built.

OOPS

Let us first clear the basic concepts ...

What is OOP?

understand the object orientation, let’s take your “hand” as an example. The “hand” is a class. Your body has two objects of type hand, named left hand and right hand. Their main functions are controlled/ managed by a set of electrical signals sent through your shoulders (through an interface). So the shoulder is an interface which your body uses to interact with your hands. The hand is a well architected class. The hand is being re-used to create the left hand and the right hand by slightly changing the properties of it.

What is an Object?
An object can be considered a "thing" that can perform a set of related activities. The set of activities that the object performs defines the object's behavior. For example, the hand can grip something or a Student (object) can give the name or address.
In pure OOP terms an object is an instance of a class. 

What is Class?
 A class is simply a representation of a type of object. It is the blueprint/ plan/ template that describe the details of an object. A class is the blueprint from which the individual objects are created. Class is composed of three things: a name, attributes, and operations.
SYNTAX:
public class Student
{
}
According to the sample given below we can say that the student object, named objectStudent, has created out of the Student class.

Student objectStudent = new Student();

 

Proprties of OOPs

What is Encapsulation (or information hiding)?

Encapsulation is wrapping of data into a single unit. It is the process of keeping state and behavior of the object in a single unit and exposing public methods to act upon the state means hiding internal data of the object from the outside world.
In OOP the encapsulation is mainly achieved by creating classes, the classes expose public methods and properties. The class is kind of a container or capsule or a cell, which encapsulate the set of methods, attribute and properties to provide its indented functionalities to other classes. In that sense, encapsulation also allows a class to change its internal implementation without hurting the overall functioning of the system. That idea of encapsulation is to hide how a class does it but to allow requesting what to do.

There are several other ways that an encapsulation can be used, as an example we can take the usage of an interface. The interface can be used to hide the information of an implemented class.

IStudent myStudent = new LocalStudent();

IStudent myStudent = new ForeignStudent();

According to the sample above (let’s assume that LocalStudent and ForeignStudent are implemented by the IStudent interface) we can see how LocalStudent and ForeignStudent are hiding their, localize implementing information through the IStudent interface.

What is Abstraction ?

Abstraction is the act of identifying the relevant qualities and behaviors an object should possess without representing background details.
The importance of abstraction is derived from its ability to hide irrelevant details and from the use of names to reference objects. Abstraction is essential in the construction of programs. It places the emphasis on what an object is or does rather than how it is represented or how it works. Thus, it is the primary means of managing complexity in large programs.


What is ASP.Net ?

ASP.NET is a web application framework developed and marketed by Microsoft to allow programmers to build dynamic web sites.
ASP.NET allows you to use a full featured programming language such as C# or VB.NET to build web applications easily.