Do Loop Part #1 by Charles Carroll
To execute a code sequence more than once ASP provides:
* DO, LOOP
* WHILE, WEND
Either of these statements can be followed by UNTIL or WHILE.
DO UNTIL
…..code to be repeated…
LOOP
DO
…..code to be repeated…
LOOP UNTIL
Do Loop and Timeouts by Charles Carroll
A loop that is infinite will not run forever. IIS will timeout the script (default is 90 seconds).
Here is an infinite loop that IIS will timeout:
<%response.buffer=true%> <TITLE>doloop1.asp</TITLE> <body bgcolor="#FFFFFF"> <HTML> <% DO counter=counter+1 response.write counter & "<br>" response.flush LOOP %> </BODY> </HTML>
Here is an infinite loop that we explicitly set a timeout for:
<% response.buffer=true server.scripttimeout=20 %> <TITLE>loop2.asp</TITLE> <body bgcolor="#FFFFFF"> <HTML> <% DO counter=counter+1 response.write counter & "<br>" response.flush LOOP %> </BODY> </HTML>
It has been assumed that a timed out script was impossible to intercept, but the next lesson shows how to use the transactional aspect of an ASP script to capture this elusive condition.
Do Loop Intercept Timeouts by Charles Carroll
The transactional nature of ASP pages can be used to intercept a script timeout.
loop3.asp traps a timeout:
<%@ TRANSACTION=Required%> <% response.buffer=true server.scripttimeout=20 %> <HTML> <TITLE>loop3.asp</TITLE> <body bgcolor="#FFFFFF"> </BODY> <% DO counter=counter+1 response.write counter & "<br>" LOOP response.flush response.write "Script executed without incident" %> </HTML> <% Sub OnTransactionAbort() response.clear Response.Write "The Script Timed Out" end sub %>
loop4.asp succeeds and does not trigger the trap:
<%@ TRANSACTION=Required%> <% response.buffer=true server.scripttimeout=40 %> <HTML> <TITLE>loop4.asp</TITLE> <body bgcolor="#FFFFFF"> </BODY> <% DO UNTIL counter=400 counter=counter+1 response.write counter & "<br>" LOOP response.flush response.write "Script Exexuted without incident!" %> </HTML> <% Sub OnTransactionAbort() response.clear Response.Write "The Script Timed Out" end sub %>
