Html Agility Pack Download Web Page
Kym Wash
Assuming you're trying to access that url, of course it should fail. That url doesn't return a full document, but just a fragment of html. There is no html tag, there is no body tag, just the div. Your xpath query returns nothing and thus the null reference exception. You need to query the right thing.
right now i managed to create xpath generator(I used webbrowser for this purpose), which works fine, but sometimes I cannot grab dynamically (via javascript or ajax) generated content. Also I found out that when webbrowser control(actually IE browser) generates some extra tags like "tbody", while again htmlagilitypack `htmlWeb.Load(webBrowser.DocumentStream);` doesn't see it.
The idea is to load using the WebBrowser which is capable of rendering the ajax content and then wait till the page has fully rendered before then using the Microsoft.mshtml library to re-parse the HTML into the agility pack.
If we need to parse dynamically rendered HTML content we can use a browser automation tool like Selenium WebDriver. This works because we will be using an actual browser to retrieve the HTML page. A real browser like Chrome is capable of executing any client code present on the page thus generating all the dynamic content.
what do i do on subsequent page requests. how do i reuse the cookies that were received after the first call using asp.net. i.e i make a call to remote login page and get logged in. the remote login page sends back cookies. how do i save and keep sending then to subsequent requests without logging in??? i can't figure out how/where to save the remote cookies??
What are you trying to index, the HTML of a page? If so I'd just create some extension methods off your model type and index it through that or custom index models yourself -guides/search-navigation/NET-Client-API/Customizing-serialization/
What part of the page content are you missing when indexing? If it is content in content areas, then you can decorate the content types you want to be included in indexing a page with the IndexInContentAreas attribute and EPiServer will take care of it for you. You could even look at overriding the IContentIndexerConventions.ShouldIndexInContentAreaConvention to handle behaviour specific to your build. For more information you can look here: -guides/search-navigation/Integration/cms-integration/Indexing-content-in-a-content-area/
This method treats each h2 and content as an individual search result (to the same page) we also added an auto scroll to the content by passing the h2 as a parameter when clicking the search result link.
Currently, a large amount of information is transmitted to the user through web pages. Providing our program with the ability to do the same is a very useful functionality when it comes to automating processes.
For now, the library is Open Source and the code is hosted on -agility-pack. And we say, for now, because in the past, the author has turned some of his Open Source libraries into commercial ones.
However, with HTML Agility Pack, we can only read the HTML code of the page but it does not execute the associated JavaScript. This is a problem in current dynamic pages, where the initially loaded HTML code (which is sometimes practically empty) is modified by the JavaScript.
Awesomium can be used to render any website. By creating an instance you can navigate to the website and by using DOM API you can interact with the page as well. It is built on Chromium Embedded Framework (CEF) and provides a great API for interaction with the webpage.
ScrapySharp is an open-source web scraping library for C# programming language which has a NuGet package. Moreover ScrapySharp is an Html Agility Pack extension to scrape data structure using CSS selectors and supporting dynamic web pages.
So, it is not as resource-intensive as Selenium, however, it also supports the ability to scrape dynamic web pages. However, if ScrapySharp is enough to solve everyday tasks, for more complex tasks it will be better to use Selenium.
The considered libraries allow to create more complex projects that can require data, parse multiple pages and extract data. Of course, not all libraries were listed in the article, but only the most functional and with good documentation. However, in addition to those listed, there are other third-party libraries, not all of which have the NuGet package.
In the broadest sense, the term web scraping refers to the more or less automated extraction of information from web pages. This requires essentially two steps: First, the data must be retrieved from the web server as specifically as possible, and second, this data must be programmatically interpreted (parsed) so that the desired information can then be extracted for further processing.
Although modern websites increasingly offer APIs and many web applications use APIs for data access, web pages are usually formatted for human consumption. Technically, content data, such as the text of an article, is mixed with control data, metadata, formatting information, images, and other data. While this data is necessary for the functionality and look and feel of a website, it is rather impeding from a data extraction perspective. Therefore, suitable tools are needed to retrieve the desired information from this data medley.
In case of errors where the web server does return content, for example a custom 401 error page, this content is also accessible via the exception as follows (access to the response headers is also shown):
In contrast to using Invoke-Webrequest, this method does not set headers automatically. It is possible to specify them though, for example to set the user agent which is usually advisable, since web pages sometimes behave differently without it.
In a recent Sitecore project, I was tasked with replacing the existing video player with a new one on multiple content pages in Sitecore. I decided to use Sitecore PowerShell to perform this task. However, since it involved more than just text replacement, I had to explore other options, and I discovered a utility called HtmlAgilityPack ( -agility-pack.net/), which can be used for manipulating HTML elements such as divs, spans, and paragraphs..., among others. Below is the PowerShell script I used:
In addition, hard boundaries need not always be an HTML-oriented limitation. They can be as simple as "work with these sets of web pages", "work with this data from these web pages", "work for 98% users 98% of the time", or even "OMG, we have to make this work in the next hour, do the best you can".
Cross Site Scripting is defined as allowing a user to inject their client side script into your web page so that it is executed when other visitors land on that page. The impact of running such a script can range from simple defacement of the page to the theft of user sessions or the highjacking iof the user's browser using malware. So how does an attacker inject their script? The most common route is via unsanitised input that is stored and then displayed without being properly encoded or otherwise escaped. User input can come from a variety of sources - form fields, querystrings, UrlData and cookies being the most accessible (to the attacker). It is also possible to manipulate AJAX routines to inject one's own values into JSON or other values that will be posted to server-side code for processing.
The exception is actually only raised when you attempt to programmatically access a value that looks suspicious. The exception description is "ASP.NET has detected data in the request that is potentially dangerous because it might include HTML markup or script. The data might represent an attempt to compromise the security of your application, such as a cross-site scripting attack. If this type of input is appropriate in your application, you can include code in a web page to explicitly allow it".
From that point, you can work with the value without exceptions getting in the way. However, if you want to display the value in the page, a second line of defence intervenes: all Razor values are automatically HTML encoded when they are rendered. That means that symbols that are part of HTML syntax, such as < or >, and & are converted to their HTML entity equivalent ( and &). As a result, the symbols will be rendered to the browser rather than treated as HTML. For example, if the value obtained from Request.Unvalidated("input") was 'some text', the following will be rendered
The bottom half of the code features a very simple form that consists of one textbox, one validation message helper and a submission button. At the top of the page, there is a using directive, making the HtmlAgilityPack library available to the page. A blacklist of disallowed HMTL tag names are stored in a List. If the form is submitted, the content of the textbox is retrieved using the Request.Unvalidated method. It is then passed to an HtmlDocument object. Html.DocumentNode.Descendants returns a collection of HtmlNode objects, each representing an HTML tag in the document. They are compared to the blacklist, and if any matches are found, the submission is rejected and the user is informed of the reason for rejection.
This sample creates a JavaScript object which has a property called "text". The value of that property is set to a snippet of (harmless, in this case) script that will cause an alert to appear in the browser if it is executed. The code also features a button and an empty div called "result". When the button is clicked, the JavaScript object is serialised to JSON and posted to a page called Receiver.cshtml. Whatever Receiver.cshtml produces as output is then set as the HTML content of the empty div. So what does Receiver.cshtml do? Well, not much:
You can use VBA to extract data from web pages, either as whole tables or by parsing the underlying HTML elements. This blog shows you how to code both methods (the technique is often called "web-scraping").
Let's now show some code for loading up the HTML at a given web page. The main problem is that we have to wait until the web browser has responded, so we keep "doing any events" until it returns the correct state out of the following choices:
760c119bf3