ASP.NET Introduction

ASP.NET stands for Active Server Page Network Enabled Technologies.

ASP.NET is basically a platform/framework to build web-based application using one of the many available programming languages such as C#, VB.NET etc.

The ASP.NET is designed to work with HTTP protocol which is the most used protocol in web technologies.

It is important to realize the architecture of the ASP.NET before going ahead. The ASP.NET uses libraries which are known as FCL Framework Class Library and CLR, Common Language Runtime and a few collections of languages such as C#, VB.NET etc. The architecture of ASP.NET is therefore about three things.

• Language: - The .NET allows you to use any one of the programming languages as per the taste and skill of the developer.
• Library: - The .NET framework has some standard libraries. For web-based application, we can use web library.
• CLR: - The CLR should be considered as a platform which facilitates running code written in any one of different languages such as C#, VB.NET etc.

Characteristics of ASP.NET Framework

Code Behind Mode- It is all about separation of code and design of the application. This is very important feature which allows the developer to focus on the code or design independently. When an ASP.NET web application has file with .ASPX extension, another file is created with .ASPX.CS extension if the code is in the C# language. This is code file different from the design file.

State management- The concept of state is very crucial in the web application. When the data of web form is transmitted to server, the state of data may change. Because HTTP protocol is a stateless protocol, it is very important to store the state of data when the user clicks to another page, otherwise the data will be lost. Thus, it is very important to manage the state of data depending upon the nature of requirements.

Caching- In the programming, caching is all about keeping the data ready for use whenever user needs the data. Sometimes, user visits the same page again and again. In this situation, the page can be cached so that the retrieval time could be reduced. The pages are cached in temporary locations.

Life Cycle of ASP.NET Application

Every application has its life cycle. Understanding the life cycle is important for the ASP.NET developers. An ASP.NET application is a web application developed using .NET frameworks. The web application has several web pages. The life cycle of the application is as follows:

• When application starts, an index file or home file is executed. The request goes to the web server and Application_Start method is executed. In this method, all the global variables are initialized with their default values.
• Every time user sends request to the server, object is created such as request object, response object, context object by the server. Technically, they are known as HttpContext, HttpRequest & HttpResponse. The HttpContext is just the container for the HttpRequest and HttpResponse objects. The HttpRequest object contains information about the current request, including cookies and browser information. The HttpResponse object contains the response that is sent to the client.
• These objects are not enough to recognize the application. Therefore, server creates another object called HttpApplication
• Dispose- This is an event object which is invoked before the instance of the application is destroyed. This allows to manage resources.
• End of Application- The application is unloaded from the memory and memory is cleansed.

Page Life Cycle

When request is sent to the web server for a page by browser, several steps take place before the response is sent back to the client browser. The steps and the objects created in these steps are as follows:

1. Page Request
2. Page Start
3. Page Initialization
4. Page Load
5. Validation
6. Post back event handling
7. Page Rendering
8. Upload

Page Request

When a page is requested from the server, it checks whether the page requested is new one or it has already been requested earlier. For this, the server searches the cache. If the page is not requested before, the server compiles the page and responds. In contrary situation, the server finds the page from the cache and responds.

Page Start

In this stage, two objects are created- request object and response object. The Request object holds all the information sent to the server and the response object holds all the information sent back to the client.

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