ASP and VB Script - Introduction

Active Server Pages (ASP) allow HTML and scripts to be included in a page and be processed by the Microsoft Internet Information Server (IIS) version 3 and above, providing equivalent interactivity of a CGI program in other Web servers.

We have seen previously the ASP model and how to install the Personal Web Server (PWS) to develop and test ASP scripts. You can also see a tutorial from Microsoft on ASP. We also reviewed Visual Basic as related to Web Programming. In this tutorial we will see how to use VB Script -- a subset of Visual Basic -- to write simple ASP scripts.

VB Script setup and documentation

Before you start installing VB Script be sure you have installed the latest version of Internet Explorer (at least 5.1), for it will update and add components to Windows needed by VB Script.

The basic reference to VB Script is the Microsoft VB Script page. To setup VB Script in your machine download its latest version from Microsoft, selecting your version of Windows and language. For example for English, Windows 98, ME & NT 4 download scr56en.exe, and for Windows 2000 is scripten.exe. You should also download a copy of the VB Script documentation to your machine.

VB Script basics

VBScript has only one data type: Variant. "Beyond the simple numeric or string classifications, a Variant can make further distinctions about the specific nature of numeric information. For example, you can have numeric information that represents a date or a time. When used with other date or time data, the result is always expressed as a date or a time. You can also have a rich variety of numeric information ranging in size from Boolean values to huge floating-point numbers. These different categories of information that can be contained in a Variant are called subtypes. Most of the time, you can just put the kind of data you want in a Variant, and the Variant behaves in a way that is most appropriate for the data it contains." (Microsoft)
Declaring VBScript Variables: we have seen that there is only one data type (Variant). The variables can be declared using Dim, Public or Private as in Visual Basic, and have two main scope levels: procedure-level or script-level.
VBScript Operators: VBScript has a full range of operators, including arithmetic operators, comparison operators, concatenation operators, and logical operators.
Decisions and Looping: the same commands available in Visual Basic.
Procedures: again, VB Script uses the same Sub and Function procedures.
VBScript Coding Conventions: conventions for variable names, scope, objects, comments and program documentation.

VB Script and ASP

Define at the top of the page to be saved as .asp the default script language as follows:

<%@ LANGUAGE = "VBScript"%>

Active Server Pages recognize script commands entered between the pair <% %> . In this format it handles code, but not necessarily it will produce output, you need to explicitly use output commands in order to produce output. When you use the pair <%= %> any variable, function will produce automatically output. Here are two simple examples displaying Hello! in the browser:

<% Response.Write("Hello!") %> ----> explicit output

<%= "Hello!" %> ----> implicit output

We will see and discuss four examples in order to understand how VBScript is used within the ASP tags.

The first example is our "old friend" Hello World! script:
hello.asp
<%@ LANGUAGE="VBSCRIPT"%>
<html>
<head>
<title>Hello World</title> </head>
<body bgcolor="White">
<div align="center"><h1>Hello World</h1></div>
<br><p><hr><p>
<%Response.Write("Hello World!")%>
</body>
</html>
As you can see we used the explicit ASAP tags to have Hello World! sent to the browser and everything else is HTML.
Our second example shows how an ASP page URL replaces the CGI program in a form:
formasp.html
<html>
<head>
<title>Form with ASP</title>
</head>
<body bgcolor="White">
<div align="center"><h1>Forms with ASP</h1>
<form method="POST" action="http://L500/decode.asp">
Name: <input type="text" name="name" size="60" maxlength="80"><br>
<input type="submit" value="Submit"><input type="Reset" value="Reset"></div>
</form>
</body>
</html>
The third example is a little more interesting showing how a function is defined and used, as well as, how you can make decisions in your script:
time.asp
<%@ LANGUAGE="VBSCRIPT"%>
<HTML>
<HEAD>
<TITLE>Date and time ASP Page</TITLE>
</HEAD>
<BODY>
<% Private Function Hello()
Dim timNow
timNow = Time
   If timNow <= CDate("12:00:00") Then
     Hello = "Good morning"
   ElseIf timNow <= CDate("18:00:00") Then
     Hello = "Good afternoon"
   Else
     Hello = "Good evening"
   End If
End Function%>
<div align="center"><%= Hello %>! Today is <%= Date %> and the day and time are <%Response.Write Now%></div>
</BODY>
</HTML>
Please note that once I opened the first tag <% I could start writing the script, almost as if I was writing a VB program not a VBScript. Please note that Time and Now are VBScript functions, not variables I created. Please also note that I used as the return value -- Hello -- the name of the function.
The line <div align="center"><%= Hello %>! Today is <%= Date %> and the day and time are <%Response.Write Now%></div> does two interesting things:
- First, it outputs the value of my Hello function and the VBScript Date function implicitly.
- Second it writes explicitly to the browser the value of the VBScript function Now (date and time).
The final example is the Fahrenheit to Celsius conversion program we saw first in Perl:
convcelsius.asp
<%@ LANGUAGE="VBSCRIPT"%>
<html>
<head>
<title>convert to Celsius</title>
</head>
<body bgcolor="White">
<div align="center"><h1>Convert to Celsius</h1></div>
<br><hr></p><p>
<% Dim sFahrenheit, sCelsius, strMethod
strMethod = Request.ServerVariables("REQUEST_METHOD")
If strMethod = "GET" Then
Response.Write "<html>"
Response.Write "<head>"
Response.Write "<title>Input of convert</title>" Response.Write "</head>"
Response.Write "<body bgcolor=White>"
Response.Write "<form action=convcelsius.asp method=Post>"
Response.Write "<p>Please enter the degrees in Fahrenheit: <input type=text name=txtFahrenheit size=6 maxlength=6></p>"
Response.Write "<input type=submit value=Submit><input type=Reset>"
Response.Write "</form></div>"
Response.Write "</body>"
Response.Write "</html>"
Else
sFahrenheit = CSng(Request.Form("txtFahrenheit"))
sCelsius = round((5 / 9 * (sFahrenheit - 32)),1)
Response.Write (sFahrenheit & " degrees Fahrenheit are " & sCelsius & " degrees Celsius")
End If %>
</BODY>
</HTML>
This example was written in a very similar way a CGI program in Perl is written. Note the following:
- The variable strMethod will allow testing if the method is GET or POST. If the method is GET then the form is sent, else the method is POST and degrees in Fahrenheit are converted to Celsius.
- Respose.Write "... was used in a similar way Print "... is used in Perl to generate HTML to the browser.
- When method was POST Request.Form( ) was used to obtain the value of the fields in the form -- the value entered in the txtFahrenheit form field.
- Input from forms on the Web are text and need to be converted to other formats as needed. In the case txtFahrenheit was converted to numeric in order to allow arithmetic operations using its corresponding numeric value sFahrenheit.
- Finally, note how output mixing text and variables was created using Response.Write.

ASP Objects

It is beyond the scope of this tutorial the detailed description of the various ASP objects. You can read a brief introduction to the subject on this tutorial.

You can see other examples of VB Script used with ASP at the Microsoft site, or other sites on the Web, like this or this other one.

This page is maintained by Al Bento who can be reached at abento@ubalt.edu. This page was last updated on November 26, 2004. Although we will attempt to keep this information accurate, we can not guarantee the accuracy of the information provided.