I need to get information from couple of web sites . For example this site
What would be the best way to get all the links from the page so that the information could be extracted.
Some times need to click on a link to get other links inside that.
I tried Watin and I tried doing the same from within Excel 2007 with Web Data option.
Could you please suggest some better way which I am not aware of .
Ncrawler might be very useful for the deep level crawling . You could also set the MaxCrawlDepth for specifying the same.
Have a look at WGet. It is an incredibly powerful tool for mining the content of a single page or an entire website. The options available allow you to dictate how many levels deep to follow in terms of links, what to do with static resources such as images, how to handle relative links, etc. It also does a very good job of mining pages which are generated dynamically, such as those served by CGI or ASP.
It's been around for many years in the 'nix world but executables compiled for Windows are readily available.
You would need to kick it off from .NET using Process.Start but you could then pipe the results into multiple files (which mimic the original website structure), a single file, or into memory by capturing standard output. Then you can do subsequent analysis such as extracting HREF HTML elements (if it is only links you are interested in) or grabbing the sort of table data evident in the link you provide in your question.
I realise this is not a 'pure' .NET solution but the power WGET offers more than compensates for this, in my opinion. I have used it myself in the past, in this way, for exactly the sort of thing I think you are trying to do.
I recommend to use http://watin.org/. This is much simpler than wget :-)
Related
What's the best way to scrape a web page that has AJAX/dynamic loading of data?
For example: scraping a webpage that presents 20 images on load, but when a user scroll down the page it loads more images (sort of like Facebook). In such a case how do you scrape all the images, not just the first 20?
This is something that not even the major search engines have mastered yet. It's called "event-driven crawling".
Google even has a guide on what to do to help them crawl your ajax sites better
Best thing would be to read some open source crawlers and see what they do. But your chances of crawling even 80% are slim at best, unless you have a specific target in mind.
There are also some interesting reads at crawljax
Basically, You should try looking for scripts and checking if they make any ajax calls, then determine what kind of parameters they take and make repeat calls with incremented/decremented parameter values. This only works if the parameters have a logical pattern, such as being numbers, single letters etc. It also depends on whether you're targeting a known site or just sending it into the wild. If you know your target you can inspect it's DOM and customize your code for greater accuracy as mentioned by wolf.
Good luck
Use a tool such as Fiddler or WireShark to inspect the web request that is done when loading more items.
Then replicate the request in your code.
Update (thanks to pguardiario ofr his comment):
Note that Wireshark is a low level network capture tool that offers a great deal of detail about the traffic (packets being exchanged, DNS lookps, and so on), and may be painful to use in such scenario, where you only wish to see the HTTP Requests.
So, you're better off using Fiddler, or a similar tool in a browser (ex: Chrome's Network inspect panel).
Crawljax is open source and can dynamically crawl Ajax-based content.
First of all, I hope my question doesn't bother you. I really need to get and idea of how I can accomplish that, but unfortunatelly, I'm really a beginner, I'm crawling when it comes to programming. I'm struggling to learn it the best way I can. I'll thank you for any help you give me.
Here's the task: I was ordered to find a way to collect some data from a website using a c# application. This will be done everyday, in order to update the data which we'll use to calculate some financial index.
I know my question might sound vague, anyway, even telling me how I can be more precise will help me. I know I seem to know desperate, but putting appart all the personell issues, my scholarship kind of depends on it.
Thanks in advance! (Please, don't mind the bad English, I'm brasilian and my English might not be that good yet.)
First, your English is fine. In fact, I thought you were a native speaker until you said otherwise.
The term you're looking for is 'site scraping'. Observe this question: Options for HTML scraping?. The second answer points to an HTML agility pack library you can use.
Now, there are two possibilities here. The first is you have to parse the HTML and scrape your data out of it. This is more computationally intensive and depends on the layout of the page. If they change the way the site looks, it could break the scraper.
The second possibility is they provide some XML or JSON web service you can consume. In this case you aren't scraping anything, but are rather using a true data feed. If the layout of the site changes, you will not break. Whether your target site supports this form of data feed is up to the site.
If I understand your question, you're being asked to do some Web Scraping, where you 1) download the contents of a web page and 2) try to parse data from that content.
For step #1, you should look into using a WebClient object in C# to download the HTML from the web page. You can give a WebClient object the URL you want to download the content from and obtain a String containing the content (probably HTML) of the URL.
How you go about doing step #2 depends on what content is present at the web site. If you know of certain patterns you're looking for in the HTML, you can search the HTML string using various methods. A more general solution for parsing HTML data can be found through using the Html Agility Pack, which will let you handle the HTML as a tree structure (DOM).
Use the WebClient class to get the page.
Turn the html into xml.
Use XPath to select the data you are interested in.
Ok, this is a pretty straightforward app design, and a lot of the code exists that you can reuse. Since you're a beginner, I'll break down into steps of what you need to do and recommend approaches.
1) You will use classes from System.Net to pull the web pages (WebClient being the easiest to usse). You will want to have this part of the program run on a timer if you can (using the scheduled jobs feature of the OS) and have it just pull the pages and drop them in a folder.
2) You have a second job which will run separately, pulling unread files from that folder, parsing them (using the HtmlAgility pack library is best) and then storing them in an index of some kind (Lucene is best for that)
3) You have a front end application of some sort (web or desktop) which queries that index for the information you're looking for.
Wondering if anyone knows of any open source code about contextualization via JS (javascript) or ASP.NET ? That is, contextualization of content - determining "what" content is?
Its an interesting area and I cant seem to find any previous projects on it ?
Really appreciate any help ?
Presumably you are looking to build something like a search engine that can find a relevant document in a sea of nondescript documents which do not contain any metadata, only their textual content.
Computers are notoriously bad at this kind of categorization, for the same reasons that they can identify spelling, but not grammar errors. It's a pattern matching problem that relies on human context to determine the correct solution.
Google is good at this because it relies on human behaviors to create relevance (like how many links from other sites a page has).
The closest thing I can think of that will do what you want (without actually attaching genuine metadata to each document by hand) is full text search. The Wikipedia article has several references to software that does this.
Depending on what you want to do, it may be easier to mine your page for context after the conent has been rendered. That way you are ensured that you have the context that the user is viewing the page. Here is a post to a jQuery plugin that highlights target words on a html page.
Here are some other plugins you might want to review:
quickSearch plugin
QuickSilver Search plugin
I'm looking for an algorithm (or some other technique) to read the actual content of news articles on websites and ignore anything else on the page. In a nutshell, I'm reading an RSS feed programatically from Google News. I'm interested in scraping the actual content of the underlying articles. On my first attempt I have the URLs from the RSS feed and I simply follow them and scrape the HTML from that page. This very clearly resulted in a lot of "noise", whether it be HTML tags, headers, navigation, etc. Basically all the information that is unrelated to the actual content of the article.
Now, I understand this is an extremely difficult problem to solve, it would theoretically involve writing a parser for every website out there. What I'm interested in is an algorithm (I'd even settle for an idea) on how to maximize the actual content that I see when I download the article and minimize the amount of noise.
A couple of additional notes:
Scraping the HTML is simply the first attempt I tried. I'm not sold that this is the best way to do things.
I don't want to write a parser for every website I come across, I need the unpredictability of accepting whatever Google provides through the RSS feed.
I know whatever algorithm I end up with is not going to be perfect, but I'm interested in a best possible solution.
Any ideas?
As long as you've accepted that fact that whatever you try is going to be very sketchy based on your requirements, I'd recommend you look into Bayesian filtering. This technique has proven to be very effective in filtering spam out of email.
When reading news outside of my RSS reader, I often use Readability to filter out everything but the meat of the article. It is Javascript-based so the technique would not directly apply to your problem, but the algorithm has a high success rate in my experience and is worth a look. Hope this helps.
Take a look at templatemaker (Google code homepage). The basic idea is that you request a few different pages from the same site, then mark down what elements are common across the set of pages. From there you can figure out where the dynamic content is.
Try running diff on two pages from the same site to get an idea of how it works. The parts of the page that are different are the places where there is dynamic (interesting) content.
Here's what I would do after I checked the robots.txt file to make sure it's fine to scrap the article and parsed the document as an XML tree:
Make sure the article is not broken into many pages. If it is, 'print view', 'single page' or 'mobile view' links may help to bring it to single page. Of course, don't bother if you only want the beginning of the article.
Find the main content frame. To do that, I would count the amount of information in every tag. Now, what we're looking is a node that is big but consists of many small subnodes.
Now I would try to filter out any noise inside the content frame. Well, the websites I read don't put any crap there, only useful images, but you do need to kill anything that has inline javascript and any external links.
Optionally, flatten that into plain text (that is, go into the tree and open all elements; block elements create a new paragraph).
Guess the header. It's usually something with h1, h2 or at least big font size, but you can simplify life by assuming that it somehow resembles the page title.
Finally, find the authors (something with names and email), the copyright notice (try metadata or the word copyright) and the site name. Assemble these somewhere together with the the link to original and state clearly it's probably fair use (or whatever legal doctrine you feel like applies to you.)
There is an almost perfect tool for this job, Boilerpipe.
In fact it has its own tag here though it's little used, boilerpipe. Here's the description right from the tag wiki:
The boilerpipe library for Java provides algorithms to detect and remove the surplus "clutter" (boilerplate, templates) around the main textual content of a web page.
The source is all there in the project if you just want to learn the algorithms and techniques, but in fact somebody has already ported it to C# which is quite possibly perfect for your needs: NBoilerpipe.
BTE (Body Text Extraction) is a Python module that finds the portion of a document with the highest ratio of text to tags on a page.
http://www.aidanf.net/archive/software/bte-body-text-extraction
It's a nice, simple way of getting real text out of a website.
Here's my a (probably naive) plan of how to approach this:
Assuming the RSS feed contains the opening words of the article, you could use these to locate the start of the article in the DOM. Walk back up the DOM a little (first parent DIV? first non-inline container element?) and snip. That should be the article.
Assuming you can get the document as a XML (HtmlAgilityPack can help here), you could (for instance) grab all descendant text from <p> elements with the following Linq2Xml:
document
.Descendants(XName.Get("p", "http://www.w3.org/1999/xhtml"))
.Select(
p=>p
.DescendantNodes()
.Where(n => n.NodeType == XmlNodeType.Text)
.Select(t=>t.ToString())
)
.Where(c=>c.Any())
.Select(c=>c.Aggregate((a,b)=>a+b))
.Aggregate((a,b)=>a+"\r\n\r\n"+b);
We successfully used this formula for scraping, but it seems like the terrain you have to cross is considerably more inhospitable.
Obviously not a whole solution, but instead of trying to find the relevant content, it might be easier to disqualify non-relevant content. You could classify certain types of noises and work on coming up with smaller solutions that eliminate them. You could have advertisement filters, navigation filters, etc.
I think that the larger question is do you need to have one solution work on a wide range of content, or are you willing to create a framework that you can extend and implement on a site by site basis? On top of that, how often are you expecting change to the underlying data sources (i.e. volatility)?
You might want to look at Latent Dirichlet Allocation which is an IR technique to generate topics from text data that you have. This should help you reduce noise and get some precise information on what the page is about.
Is there anything I can do while coding in Asp.net to make my website come on top in search engines for general keywords? (For example : cars...assuming that my site is wwww.joshautos123.com)
Thanks
This has nothing to do with ASP.NET Josh,
You need to start investigating SEO in general (Search Engine Optimization)
This is a pretty broad topic (more info here) covering everything from keywords, content, url formatting, and cross linking to lots of different sites/resources.
The best thing you can do if your only developing it (and not responsible for marketting)
is that you put together a well designed, clean, standards compliant site.
you can follow the search engine optimization guidlines for your header, images etc.
that the way you can acheive it.
Anyways, you can read this tutorial, it will help you.
for more, you can create a good master page with good meta tages. it will help you...
This sounds a bit "black hat" to me.
The most important aspect of SEO is content, So as long as you have lots of good, meaningful content relating to "cars" you stand a good chance.
Next up, you want lots of reliable sources to link to you with meaningful keywords in the links. And a whole bunch more SEO tricks
When making the ASP.NET application, you can make sure you facilitate SEO best practices, but at the end of the day, if your site is full of nonsens and people don't think it's worth linking to. Your'e not going to get very good rankings.
Most of the SEO enhancements can be done beside of asp.net.
so just add the right tags and words to the aspx file.
or for dynamic pages, generate them from the content.
but what you should have also in mind are 2 things:
first of all, run all of your system under one url. and all other ones should be redirected with 301 to it (e.g. redirect http://joshautos123.com to www.joshautos123.com with 301 redirect)
and do not use subdomains for different parts (that will split your search rank)
and second, you should use the asp.net mvc.
because one important part of seo is, that the right content (e.g. titles, real car names, etc) are in the URL.
rest was already said by the other answers....
Try visiting this website for a start Using Meta Tags with Master Pages in ASP.NET