Within the context of Web-based processing, a set of Visual Basic statements is often called as a script.
A D V E R T I S E M E N T
A Visual Basic program is a set of commands, coded in special syntax of the language, that causes the computer to perform some type of processing to generate information where none has existed before.
These commands, or statements, are arranged in the logical order so that the computer can carry out the processing in a step-by-step sequence.
Loading of Vb.NET Code
Wherever they appear, Visual Basic scripts are processing routines called upon by
the Web page to carry out its processing activities and to produce the output results for display on the page.
Visual Basic code can be physically located in the two places.
Code can appear on the Web page itself; it can also appear in a separate file that is accessible from
the Web page.
Script Blocks
A script block is simply the section of the page surrounded by <script> tags in the following format.
It must be enclosed within an identifiable script block,when Visual Basic code appears on a Web page,
A script block can appear anywhere on the Web page, and there can be as many
script blocks as the user needed. However, a single script block is normally the sufficient one,
and it commonly appears at the top of the Web page, prior to any HTML
code that appears on the page. The reason for the placing the script at the top of
the page is in recognition of the fact that the server runs the script first,
before it takes action on any other components of the Web page.
The attribute runat="server" indicates that the
enclosed script is to be run, or executed, by Web server computer
prior to transmitting the page to the client computer which made the URL request
for the page and the attribute also differentiates server scripts from
browser scripts that also are enclosed within <script>
tags.In the JavaScript language,these browser-based scripts are usually written.
Optionally, language="vb" or language="Visual Basic" can be included in the opening tag to indicate
the programming language used in the script and this attribute is optional since
Visual Basic is the default server language for Web page scripts.
Subprograms
Although the topic of subprograms and other similar containers is covered later in these tutorials and one particular subprogram can provide the wrapper for the statements introduced over the next several tutorials. The Page_Load subprogram is the one that the server first runs when the Web page is opened. Any statements can be placed inside this subprogram for immediate execution. A general script setup to run Visual Basic statements, then, is shown by the following outline.
A script block is the enclosing container for all Visual Basic statements on a page and however, most statements must be enclosed inside another programming structure in order to be executed properly. This structure is a named container that can be called upon to perform the processing given by its enclosed statements. The most common container for statements is a subprogram.
<script runat="server">
Sub Page_Load
...Visual Basic statements
End Sub
</script>
Code-Behind Files
There are slight coding differences between an an external class and internal script and a Web-page script is supplied with various default language settings that must be made explicit when coding a formal Visual Basic class. These differences are pointed out later in the tutorials and when learning the Visual Basic language it is best to develop Web pages with on-page scripts to remove the complexities of constructing classes.
The second location for Visual Basic code is in a separate code-behind file and this file contains only Visual Basic code packaged as a Visual Basic class. The file name is always given the extension .vb to indicate a Visual Basic program.
