By Pawan Kapoor, Sumit Goel

(This paper is a prize winning entry at Literati 2002 )

INTRODUCTION:

ASP stands for ‘Active Server Pages’ which run inside the IIS(Internet Information Server).ASP is a microsoft technology. To run IIS you must have window NT4 or later.

An ASP file name has an extension ‘.asp’. It may contain HTML and coding in languages such as PERL,J-SCRIPT,VBSCRIPT. Any file with the above extension is treated as an ASP file by the windows and it uses ASP engine to execute the file.

Basic ASP Syntax

An ASP file can contains HTML tags, just as a standard HTML file. In addition , an ASP file can contain server scripts surrounded by delimiters ‘<% %>’.

Server scripts are executed on the server and can contain any expression , statement , procedures and operators valid for the language used for the coding.

ASP: Over and above HTML

ASP pages score over normal HTML pages as they can dynamically edit , add or remove any content of a web page , respond to user queries or data submitted from the HTML forms, access any data from the data bases and return the results to the browser , provide security since the ASP code cannot be viewed from the browser i.e. when the source of a web page is viewed the HTML equivalent of the ASP page is shown and the coding is hidden from the user . Various sites incorporating dynamic features are designed using ASP.

Design of an ASP Page:

An ASP Page may consists of two parts:

• 1: The plain HTML: Similar to that in .html files . This portion of the page is responsible for the appearance of the page.

• 2: The coding part: This part is responsible for adding dynamic features to the pages and may contain code in several languages as PERL,JSCRIPT and VBSCRIPT.

To Call an ASP Page:

In order to execute an ASP page the name of the ASP file is to be typed in the address bar of the browser as URL(Unique Resource Locator).

The IIS finds the page and passes the request to the ASP engine. The ASP engine reads the FILE line by line, and executes the scripts in the file. Finally the ASP file is returned to the browser as Plain HTML.

AN INTRODUCTION

ASP.NET is Microsoft's next generation of Active Server Pages. It's Microsoft's flagship technology for building Web sites. You can use ASP.NET to build large scale commercial Web sites or small company intranets. The technology was designed to be easy to use, but very scalable. The ASP.NET files have an extension as ‘aspx’. Declaring an ASP page file with ‘aspx’ extension will make it behave as an ASP.NET page.


ASP.NET over and above ASP

ASP.NET and Active Server Pages ASP.NET is descended from Active Server Pages. However, it's such an evolutionary advance that the two technologies are only dimly related.

Here are some of the key benefits of ASP.NET over ASP:

• 1:ASP.NET Pages are Compiled When an ASP.NET page is first requested, it is compiled and cached on the server. This means that an ASP.NET page executes very quickly.
• 2: ASP.NET Pages are Built with Server Controls classes.You can easily build complex Web pages by assembling the pages out of ASP.NET server controls. For example, by adding validation controls to a page, you can easily validate form data Or, by adding a DataGrid control to a page, you can easily display database data.
• 3: Whereas ASP Classic pages are created with scripting languages such as VBScript and JScript, ASP.NET pages are created with full-blown programming languages such as Visual Basic (Application, Session, and Server objectsand C#Request, , there are over .. And whereas there are five standard objects available in the ASP Classic Framework the )Framework that you can use in an ASPResponse,
  3,400 standard objects in the .NET NET page.
• 4: Browser Independence: Very often page layouts of ASP pages needs to be formatted according to the browser that’s presenting the pages, which often results in writing different sets of codes for different browser. This is something any developer would like to get rid of . CLR(Common Language Runtime) automatically checks from the http request headers what type of browser is making the request and can generate a page tailored to that browser. This brings in better browser compatibility.

Surprisingly, given all the power and flexibility packed into ASP.NET. ASP.NET is much easier to use than ASP Classic. By adding a few server controls to a page, you can build sophisticated
page in minutes that would take days to develop with ASP Classic.

DESIGN OF AN ASP.NET PAGE

ASP.NET Page typically contains two sections:

• 1:Code Declaration Block: The code declaration block contains all the subroutines and functions that you want to execute in the page.
  
• 2:Code Render Block :The code render block is executed when the ASP.NET page is requested and actually rendered to a Web browser.
  For example, the ASP.NET page in Listing 1.0 was written with Visual Basic.

Listing 1.0 - Simple.aspx

<Script Runat="Server">
Sub Page_Load
myLabel.Text = DateTime.Now()
End Sub
</Script>

<html>
<head><title>Simple.aspx</title></head>
<body>

<asp:Label
ID="myLabel"
Runat="Server" />

</body>

</html>

The Code Declaration Block:

The code declaration block in Listing 1.0 is the part of the page that starts with the <Script Runat="Server"> tag and ends with the closing </Script> tag. In the listing above, it contains a single subroutine named Page_Load that executes whenever the page is requested.The Page_Load subroutine assigns the current date and time to the Text property of a Label control.

The Code Render Block :

The code render block consists of the remainder of the page below the code declaration block. You'll notice that the majority of the code render block is plain old HTML.

The code render block contains a single ASP.NET server control. The Label control is declared with the following server-side tag:

<asp:Label
ID="myLabel"
Runat="Server" />

ON LOADING AN ASP PAGE

Whenever an ASP.NET page is requested, a sequence of events are raised:

Init - The first event raised when a page is requested .

Load - This event is raised before any events are raised by controls contained in the page.

PreRender - This event is raised after any events are raised by controls contained in the page.

UnLoad - This event is raised when the page is unloaded from memory.

Disposed - This event is raised when the page is released from memory.

You can create subroutines to handle any of these events. For example, to handle the Load event, you would create a subroutine that looks like this:

<Script Runat="Server">

Sub Page_Load

</Script>

Notice that you handle the page's Load event by creating a subroutine named Page_Load. You handle the Init, Load, PreRender, UnLoad, and Disposed events with Page_Init, Page_Load, Page_PreRender, Page_UnLoad, and Page_Disposed subroutines.

By far, the most useful page event is the Load event. Typically, you handle this event to assign values to controls in a page. For example, you would handle this event to assign a value to a Label control or assign database data to a DataGrid control.

Thus each of these events can be called based upon the demand of word done by the web-page.

Food For Thought:The important difference between the Load and PreRender events is that the Load event is raised before any events are raised by controls contained in the page.

For example:If a .NET page contains a subroutine to handle a Page Load event, a Button Click event, and a Page PreRender event. On clicking the button, the Page_Load subroutine is executed before the Button_Click subroutine and the Page_PreRender subroutine is executed after the Button_Click subroutine.

YOUR FIRST ASP.NET ASSIGNMENT

Way back when programming was new, someone decided that the first thing you should do whenever you start programming in a new environment or language is print out "Hello World." I have no idea who it was that came up with this idea or why it stuck, but it has. Not being one to fight the system without reason, we'll be using this incredibly simple idea as the basis for our first ASP.NET page. We will consequently discuss various server controls available in the .NET through the example.

Lets deal with an HTML page which prints ‘hello world’

helloworld.html
<html>
<
>
<title>ASP.NET Hello World</title>

</head>

<body bgcolor="#FFFFFF">

<p>Hello World!</p>

</body>
</html>

Now let's try it in ASP.NET.

Hello World in ASP.NET

Fundamentally, there's no requirement that an ASP.NET page (sometimes referred to as a Web Form) actually do any processing. As such, the simplest way to get the task at hand accomplished is to take the existing HTML page listed above and simply give it an aspx extension. This results in a perfectly legal and acceptable ASP.NET page. The only thing that happens when you do this is that you tell the web server to pass the aspx file through the ASP.NET runtime, which in turn compiles it and processes any code it finds (in this case none) before it returns the result to the client.

helloworld.aspx
<html>
<head>
<title>ASP.NET Hello World</title>
</head>
<body bgcolor="#FFFFFF">

<p>Hello World!</p>

</body>
</html>

Now move to a version which does some processing:

The Classic ASP Way One of the nice things about ASP.NET
is that it will work with a lot of classic ASP style code with only minor changes.

helloworld2.aspx
<%@ Page Language="VB" %>

<html>
<head>
<title>ASP.NET Hello World</title>
</head>
<body bgcolor="#FFFFFF">

<p><%= "Hello World!" %></p>
</body>
</html>

The code listed above probably seemed pretty familiar to most people, but it illustrates one of the major limitations of classic ASP scripting. In order to get the phrase "Hello World!" in between the two paragraph tags, you had to place the code that outputs the phrase where you want the phrase to appear. This makes it difficult to maintain any sort of structure and is a chief contributor to much of the so called "spaghetti code" that developers ended up writing.

Using Server Controls - HTML Controls

This time around, we're going to introduce what is called a server control. You can think of a server control as HTML tags for the server. Regular HTML tags are read by the browser and interpreted in some way determined by what they contain. The same happens on the server with server controls, and the first type of server control, called HTML Controls, look very much like a standard HTML tag. The only difference is that they contain a special runat="server" attribute. You can see an example illustrated in the code listing below:

helloworld3.aspx
<%@ Page Language="VB" %>
<%
HelloWorld.InnerText = "Hello World!"
%>

<html>
<head>
<title>ASP.NET Hello World</title>
</head>
<body bgcolor="#FFFFFF">
<p id="HelloWorld" runat="server"></p>

</body>
</html>
Notice how the same <p> tag from our original document has now become an active part of the processing of the page. We've given it the runat="server" attribute which turns it into a web control. We've also given it an id attribute so we have a way to reference it
from the code sections of your page. Notice that the end result of this code is that the section that actually specifies the text to write out has been moved into a code section of the page and this code section can be placed anywhere (ie. not at the point of display!).


Using Server Controls - Web Controls

Web controls are the second type of server control. They are similar to HTML controls, but tend to be more complex and do not necessarily map directly to any one HTML tag. This allow them to be much more flexible and useful. Their object model also is usually more complex. Where HTML controls tend to have object models that mirror their HTML tag counterparts, web controls usually have more abstract or "high-level" properties and methods.

helloworld4.aspx
<%@ Page Language="VB" %>
<%
HelloWorld.Text = "Hello World!"
%>
<html>
<head>
<title>ASP.NET Hello World</title>
</head>
<body bgcolor="#FFFFFF">
<p><asp:label id="HelloWorld" runat="server" /></p>

</body>
</html>

The only thing that's changed from the previous listing is the control we're using. We've restored the original <p> tag so it's now once again a plain old HTML tag and is entirely ignored by the server and have placed an <asp:label> tag inside of it. This new tag is now the focus of our code that sets the text to "Hello World!". Notice how the property has changed from InnerText to simply Text. This is because the <asp:label> tag object model is defined differently from that of the HtmlGenericControl we were using before.

ABSTRACT

In this paper we will give an insight into a revolutionary programming framework named as Microsoft.NET through one of its applications ASP.NET.

The new platform developed by Microsoft enables rapid development of powerful web applications and services which promises to bring revolution in the present scenario of web programming.

Paper takes a modular approach to apprehend the above said by first exploring ASP and then maturing to the latest .NET platform.

The points of distinction of .NET and its ASP predecessor are taken on extensively.

Paper does equal justice to the much necessary control classes introduced in the .NET platform as an unique feature.

The paper finally concludes with a simple example which gives enough reason to believe the excellence of .NET over other platforms by clearly comparing the features in each of the setups.

CONCLUSION

To conclude ASP.NET may be truly titled as something which will redefine web and make web applications faster in years to come with ease in coding.

Overall the ASP.NET framework looks very promising .

We feel it’s a right opportunity for developers to equip themselves with this amazing framework.

It provides minimal learning curve for object oriented developers and is a powerful framework for developing and deploying next generation web applications.

ASP.NET is sure to have a significant impact on web application developments in the years to come.