I'm trying to get the list of requests that occur within the confines of a single httpwebrequest from my aspx page.
When using fiddler, you request a page from IE. While doing that request the page requests x number of other files as part of the request. Fiddler shows you that you are getting a .css file, a .js file and maybe its's also requesting a couple other pages from that page before it renders.
I want to be able to make the httpwebrequest from my aspx page then monitor (or list out) the URLs that are being called within that request.
That said I am open to alternate ways to do the request. e.g. IFRAME, etc.
Maybe this just can't be done from an aspx page. Ideas?
If you are using an HttpWebRequest on the server, it is not going to download all of the other embedded resources. If you want to get the list of resources used on the page, you'll have to parse the HTML yourself.
Here's a related questions that might be useful: How can I use HTML Agility Pack to retrieve all the images from a website?
This cannot be done from ASPX page. I think you should hook on one of the Global ASAX events (via writing custom HttpModule) and intercept the requests there.
Related
I want to download content of one website programatically and it looks like this content is loaded by ajax calls. When I simply disable javascript in my browser, only 1 request is made by this page and all content is loaded without AJAX.
What I need to achieve is to make a web request which will tell web page that I have disabled javascript so it returns me all the content and not just empty body tag with no content at all.
Any suggestions how to do that?
You need to mimic browser.
Steps:
Use Fiddler and see what is sent by browser.
Set the same headers/cookies/user agent via C# code.
If does not work - compare request your code makes with browser's one by using Fiddler as proxy for your C# code (set proxy to http://localhost:8888)
Using a httpmodule I want to add a meta tag to all pages in my web application at run time. So I need to access the header section of my page. How can I do this in a httpmodule?
You would be better served by inserting this META tag into the header of your site's Master Page (and creating and using a Master Page if you don't already have one.) That give's you a central location for it, while not having the overhead of a module in the pipeline.
If you need to use an HttpModule, see this link about installing a response filter.
You probably want the HttpApplication and the current context of that so you can modify the request and response streams.
I've application that uses another web sites data so how can i get it because it uses some JavaScript functions to get that data and it not show in page view-source.
Check the NET tab in firebug, XHR and check the resource that is requested, and request the same resource.
Basically you have to render the webpage and ensure the javascript functions are run (evaluated). You could do this by "borrowing" their javascript files (by linking to them from your own page), but this may not work as you don't know what's in those files - they could be accessing DOM elements that you don't have in your page, or calling to other domains which may prevent them from working correctly.
The easiest way to show the same data is to just host the page inside an iframe on your own page. If you are looking to do this from a normal client application (i.e. not a web app) then you will need a browser control that you navigate to the target page. If the browser control is invisible you could then scrape values from it and show them in your app, although this is a very clumsy way to do it, and it's debatable about how ethical it is.
If you want the another web site view source use the HTTPWebRequest to get the response stream in c#.
I have an idea for an App that would really help me out in work but I'm not sure if it's possible.
I want to run a C# desktop application that will ask for a value. When a value is supplied, the application will open a browswer, go to a webpage and add the value into a form on an online website. The form is then submitted and a new page is loaded that contains a table of results. I then want to extract the table of results from the page source and write code to parse the result values.
It is not important that the user see's this happen in an actual browser. In other words if there's a way to do it by reading HTTP requests then thats great.
The biggest problem I have is getting the values into the form and then retrieving the page source after the form is submitted and the next page loads.
Any help really appreciated.
Thanks
Provided that you're only using this in a legal context:
Usually, web forms are sent via POST request to the web server, specifically some script that handles it. You can look at the HTML code for the form's page and find out the destination for the form (form's action).
You can then use a HttpWebRequest in C# to "pretend you are the form", sending a POST request with all the required parameters (adding them to the HTTP header).
As a result you will get the source code of the destination page as it would be sent to the browser. You can parse this.
This is definitely possible and you don't need to use an actual web browser for this. You can simply use a System.Net.WebClient to send your HTTP request and get an HTTP response.
I suggest to use wireshark (or you can use Firefox + Firebug) it allows you to see HTTP requests and responses. By looking at the HTTP traffic you can see exactly how you should pass your HTTP request and which parameters you should be setting.
You don't need to involve the browser with this. WebClient should do all that you require. You'll need to see what's actually being posted when you submit the form with the browser, and then you should be able to make a POST request using the WebClient and retrieve the resulting page as a string.
The docs for the WebClient constructor have a nice example.
See e.g. this question for some pointers on at least the data retrieval side. You're going to know a lot more about the http protocol before you're done with this...
Why would you do this through web pages if you don't even want the user to do anything?
Web pages are purely for interaction with users, if you simply want data transfer, use WCF.
#Brian using Wireshark will result in a very angry network manager, make sure you are actually allowed to use it.
I'm using a C# WebClient to post login details to a page and read the all the results.
The page I am trying to load includes flash (which, in the browser, translates into HTML). I'm guessing it's flash to avoid being picked up by search engines???
The flash I am interested in is just text (not an image/video) etc and when I "View Selection Source" in firefox I do actually see the text, within HTML, that I want to see.
(Interestingly when I view the source for the whole page I do not see the text, within HTML, that I want to see. Could this be related?)
Currently after I have posted my login details, and loaded the HTML back, I see the page which does NOT show the flash HTML (as if I had viewed source for the whole page).
Thanks in advance,
Jim
PS: I should point out that the POST is actually working, my log in is successful.
Fiddler (or similar tool) is invaluable to track down screen-scraping problems like this. Using a normal browser and with fiddler active, look at all the requests being made as you go through the login and navigation process to get to the data you want. In between, you will likely see one or more things that your code is doing differently which the server is responding to and hence showing you different HTML than a real client.
The list of stuff below (think of it as "scraping 101") is what you want to look for. Most of the stuff below is probably stuff you're already doing, but I included everything for completeness.
In order to scrape effectively, you may need to deal with one or more of the following:
cookies and/or hidden fields. when you show up at any page on a site, you'll typically get a session cookie and/or hidden form field which (in a normal browser) would be propagated back to the server on all subsequent requests. You will likely also get a persistent cookie. On many sites, if a requests shows up without a proper cookie (or form field for sites using "cookieless sessions"), the site will redirect the user to a "no cookies" UI, a login page, or another undesirable location (from the scraper app's perspective). always make sure you capture the cookies set on the initial request and faithfully send them back to the server on subsequent requests, except if one of those subsequent requests changes a cookie (in which case propagate that new cookie instead).
authentication tokens a special case of above is forms-authentication cookies or hidden fields. make sure you're capturing the login token (usually a cookie) and sending it back.
POST vs. GET this is obvious, but make sure you're using the same HTTP method that a real browser does.
form fields (esp. hidden ones!) I'm sure you're doing this already, but make sure to send all form fields that a real browser does, not just the visible fields. make sure fields are HTML-encoded properly.
HTTP headers. you already checked this, but it may make sense to check again just to make sure the (non-cookie) headers are identical. I always start with the exact same headers and then start pulling out headers one by one, and only keep the ones that cause the request to fail or return bogus data. this approach simplifies your scraping code.
redirects. These can either come from the server, or from client script (e.g. "if user doesn't have flash plug-in loaded, redirect to a non-flash page"). See WebRequest: How to find a postal code using a WebRequest against this ContentType="application/xhtml+xml, text/xml, text/html; charset=utf-8"? for a crazy example of how redirection can trip up a screen-scraper. Note that if you're using .NET for scraping, you'll need to use HttpWebRequest (not WebClient) for redirect-dependent scraping, because by default WebClient doesn't provide a way for your code to attach cookies and headers to the second (post-redirect) request. See the thread above for more details.
sub-requests (frames, ajax, flash, etc.) - often, page elements (not the main HTTP requests) will end up fetching the data you want to scrape. you'll be able to figure this out by looking which HTTP response contains the text you want, and then working backwards until you find what on the page is actually making the request for that content. A few sites do really crazy things in sub-requests, like requesting compressed or encrypted text via ajax, and then using client-side script to decrypt it. if this is the case, you'll need to do a bit more work like reverse-engineering what the client script is doing.
ordering - this one is obvious: make HTTP requests in the same order that a browser client does. that doesn't mean you need to make every request (e.g. images). Typically you only need to make the requests which return text/html content type, unless the data you want is not in the HTML and is in an ajax/flash/etc. request.
(Interestingly when I view the source for the whole page I do not see the text, within HTML, that I want to see. Could this be related?)
This usually means that the discrepancy is caused by some DOM manipulations via javascript after the page has loaded. Try turning off javascript and see what it looks like.