Making posts to an ASP.NET webform.

Bernard bernard.chhun at
Mon Oct 2 16:55:23 CEST 2006

hiya everyone,

I've made this little webcrawler using BeautifulSoup, urllib and
urllib2. I've been encountering ASP.NET Forms recently and I can't seem
to make a proper post to some of them. My post function has been doing
great until this particular website.
Here's some explanations first so that you guys understands my

Usually there are 8 hidden inputs spread all over the web page:
__EVENTTARGET --> that is the id of the control that is assigned by the
ASP.NET engine. It is usually in this particular form
"dg_Result$_ctl2$linkbtn1" The javascript function DoPostback usually
replaces the '$' for a ':' before doing the real post. Some other
ASP.NET page doesn't.
__EVENTARGUMENT --> nothing's here usually.
__ScrollTop --> its value is often 0
__ScrollLeft --> same as __ScrollTop
__ValidationSummary --> usually empty
__VIEWSTATEENCRYPTED --> an encrypted string. I don't know what it
means nor what it does.
__EVENTVALIDATION --> an encrypted string. I don't know what it means
nor what it does.
__VIEWSTATE --> the encrypted state of the current control. the state
of a datagrid for example.

I extract all those values using regexes on the web page, build a
dictionnary out of all those values and encrypt the whole thing using
urllib.urlencode(). Afterwards I extract the form action and post the
whole thing with cookies enabled. This procedure works like a charm.

The website I've just encounted has only 3 of the 8 hidden inputs.
I tried posting the whole thing using only these 3 values & nada.
I then tried posting the whole thing using all empty values for the 5
remaining values...still nothing.

Has anyone tried what I'm doing? and if you tried how have you
succeeded getting the data back after the post action?

thanks for any tips!


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