Debugging ASP Pages

ASP Tutorials - Herong's Tutorial Examples

∟Debugging ASP Pages

This section provides a tutorial example on how to use MS Script Debugger and find a bug in an ASP script example page.

Now we know how to set up the ASP page to run in the debugger. Let's play the debugger with the following ASP page.

<%@ language="vbscript"%>
<!-- debug_test.asp
     Copyright (c) 2002 by Dr. Herong Yang
     This program has a create and open files as text stream 
     objects.
-->
<html><body>
<%
   response.write("<b>Calculating term deposit income</b>:<br/>")
   capital = 100
   interest = 8.0
   term = 10
   value = capital
   for i = 1 to term
     value = value * (1+interest/100)
   next
   response.write("Capital = " & capital & "<br/>")
   response.write("Interest = " & interest & "<br/>")
   response.write("# of terms = " & term & "<br/>")
   response.write("Value = " & value & "<br/>")
%>
</body></html>

Now load the ASP page to IIS and the debugger. If you put a breakpoint at the beginning of the "for" statement and request the page, IIS will execute the page and stop at the breakpoint. Here is what we can do with the debugger.

1. If you click the step over icon, IIS will execute the current statement and stop at the next statement.

2. If you want to see the value of variable "interest", you need to select Command Window from View menu. In the command window, type "? interest", you will see the value of "interest", 8, displayed.

3. Actually "?" command in the command window can be used to evaluate any expression. Try this: "? interest/100", you will get 0.08.

4. Further more, you can execute any VBScript statements in the command window. For example, "interest = 7.5" will change the value in "interest" to 7.5.