ASP Tutorials - Herong's Tutorial Notes
Dr. Herong Yang, Version 4.11

Visual Basic Script (VBScript)

Part:   1  2  3 

ASP Tutorials - Herong's Tutorial Notes © Dr. Herong Yang

hyBook - Guestbook Application

Using MS Access Databases

ActiveX Data Object (ADO)

Controlling Response Header Lines

Microsoft Scripting Runtime DLL

Using Cookies

ASP Sessions

ASP Objects

Microsoft Script Debugger

Internet Information Services (IIS)

... Table of Contents

(Continued from previous part...)

In the next example, I will show you the difference between in-line scripts and script blocks: 

<!-- output_sequence.asp
     Copyright (c) 2002 by Dr. Herong Yang
     Verifying output sequence of scripts and HTML text. 
-->
<html><body>
<script language="vbscript" runat="server">
   response.write("Text line 1.<br/>")
</script>
Text line 2.<br/>
<script language="vbscript" runat="server">
   response.write("Text line 3.<br/>")
</script>
Text line 4.<br/>
</body></html>

Output: 

Text line 2.
Text line 4.
Text line 1.
Text line 3.

Supprised? I was supprised before I learned that execution rule about script blocks mentioned in the previous section. The output also tell us that the default language on IIS 5.0 is set to VBScript. Otherwise, text line 1 and 3 would be displayed first. The problem can be avoided by using the in-line scripts: 

<%@ language="vbscript"%>
<!-- output_sequence_corrected.asp
     Copyright (c) 2002 by Dr. Herong Yang
     Verifying output sequence of scripts and HTML text. 
-->
<html><body>
<%
   response.write("Text line 1.<br/>")
%>
Text line 2.<br/>
<%
   response.write("Text line 3.<br/>")
%>
Text line 4.<br/>
</body></html>

Now you know the different ways to use VBScript in ASP pages. But which way is better?

In-line script, <%...%>, is very flexible in mixing dynamic data with static HTML text. But the syntax is not so XML friendly.

Script block, <script ...>...</script>, is not useful at all if you want to keep static HTML text in your page. It can only be used, if you want to write the entire page in a single block, and output all HTML text with response.write() calls.

Personally, I prefer script block syntax, because I could easily manipulate it with XML tools. So I will be using script blocks most of the time for my sample ASP pages in this book. Note that even HTML comment tag <!-- --> must be moved into the script blocks.

Variables and Expressions in VBScript

Special rules about variables and expressions:

  • Variables used without declarations are called "variant" variables.
  • Variant variables can be used to store different data types.
  • Variable names are case insensitive.
  • "=" is the assignment operator. But it is also the boolean equality operator.
  • "&" is the string concatenation operator.

Here is a sample ASP page, variable.asp: 

<script language="vbscript" runat="server">
'  variable.asp
'  Copyright (c) 2002 by Dr. Herong Yang
'  This program demonstrates some special rules about variables and 
'  expressions.
'
   response.write("<html><body>")
   response.write("<b>Tests on variables</b>:<br/>")
   i = 1 + 2 + 3
   s = "Sum = "
   s = s & i & "<br/>"
   i = i=6
   response.write(s)
   response.write("Is the answer correct? " & i)
   response.write("</body></html>")
</script>

Output: 

Tests on variables:
Sum = 6
Is the answer correct? True

"i = i=6" is a very unusual statement. First of all, variable "i" has changed its data type from integer to boolean. Secondly, two "=" signs are used next to each other, the first one is an assignment operation, and the second one is a boolean equality operator.

(Continued on next part...)

Part:   1  2  3 

Dr. Herong Yang, updated in 2003
ASP Tutorials - Herong's Tutorial Notes - Visual Basic Script (VBScript)