Posting to Form in Subdirectory

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Hi all. I have experience with C#/VB.NET and ASP Classic, but am very new to
ASP.NET.

I'm using ASP.NET 2.0 and am modifying a site. I copied the site files to a
subdirectory to test and (hopefully) not interfere with the live version.

I am running a page in the subdirectory that should submit to itself:
http://www.<site>.com/dev/QuoteGuestInfo.aspx. The Page directive is:

<%@ Page Language="VB" MasterPageFile="~/dev/masterfile.master"
AutoEventWireup="false" CodeFile="QuoteGuestInfo.aspx.vb"
Inherits="QuoteGuestInfo" %>

When I do a View Source on the page, I see the <formtag as:
<form name="aspnetForm" method="post" action="QuoteGuestInfo.aspx"
id="aspnetForm">

When I submit the form, I get a "The resource cannot be found." error, with
Requested URL: /QuoteGuestInfo.aspx.

So it looks like it's going to the main directory instead of my dev
subdirectory. Is there a way to make the post go back to the dev
subdirectory instead of the main dir?

(I did a search but I'm new enough on this topic I'm not quite sure what to
search on.)

Thanks for any help,
Steve