Knowledge Base Articles » KB100217: Response.Write Statements DO NOT Show Up Under IIS 5.
A common technique for quickly debugging simple ASP pages is to place Response.Write
statements at key points in the code. Then, when an error occurs in the page, the
output from all the debug statements prior to the point of failure shows up in the
browser, followed by the error message generated by the ASP interpreter. While this
method works fine under IIS 4/ASP 2.0, by default it will not work under IIS 5/ASP 3.0.
This article explains why, and describes how to make IIS 5 behave the same as IIS 4 in
Under IIS 5, when an error occurs in the processing of an ASP page, the only
sent to the browser is the error page. This is because, under ASP 3.0, the
is set to True
by default. The effect of this setting is to cause all ASP-generated output
to be buffered on the server rather than being immediately sent to the client. The
buffered output is only sent to the client when execution of the page is complete, or
an explicit call to
In the event of an error however, the ASP engine clears the buffer and sends only
the error page to the client. Thus none of the Response.Write debug statements (or
indeed any of the HTML code in the page) ever reach the browser.
Further complicating this issue, is that there is a quirk concerning the default value of
that is dependent on how Window 2000 is initially
installed on your computer.
If you do a clean install, the ASP 3.0 default value will be True
However, if the install is an upgrade, the ASP 3.0 default value will be False
(not as expected!).
Fortunately, it is an easy matter to set the buffering to be false.
While you are debugging, simply placing the following statement at the top of your ASP page:
<% Response.Buffer = False %>
For more details of the Response.Buffer property, refer to the online DevGuru
Reference which now covers ASP 3.0.