C# httpwebrequest and javascript

问题:

I am using C# HttpWebRequest to get some data of a webpage. The problem is that some of the data is updated using javascript/ajax after the page is loaded and I am not getting it in the response string. Is there a way to have the webrequest wait untill all the scripts in the page have finished executing?

Thanks

Amit

回答1:

If I correctly interpret your question, there is no simple solution for your problem.

You are scraping the HTML from a server and since your C# code is not a real web browser, it doesn't execute client scripts.

This way you can't access information which the HTML you fetch doesn't contain.

Edit: I don't know how complex these AJAX calls from the original web site are, but you could use Firebug or Fiddler for IE to see how the requests are made in order to call these AJAX calls in your C# application too. So you could add the pieces of information you'll need. But it's only a theoretical solution.

回答2:

Just an idea but there is a way to have .net load a webpage as if it were in a browser: using System.Windows.Forms

you could Load the webpage into a WebBrowser control

WebBrowser wb = new WebBrowser();
wb.ScrollBarsEnabled = false;
wb.ScriptErrorsSuppressed = true;
wb.Navigate(url);
while (wb.ReadyState != WebBrowserReadyState.Complete) { Application.DoEvents(); }
wb.Document.DomDocument.ToString()

This will probably give you the pre ajax DOM but maybe there is a way to let it run the ajax first.

回答3:

When you open a web page in a web browser, it is the browser that executes the javascript and downloads additional resources used by the page (images, scripts, etc). HttpWebRequest by itself will not do any of this, it will only download the html for the page you requested. It will never execute any of the javascript/ajax code on it's own.

回答4:

Use HttpWebRequest to download the page, programatically search the source code for the relevant ajax information and then use a new HttpWebRequest to pull that data down.

回答5:

HttpWebRequest does not emulate a web browser, it just downloads the resource you point it at. This means it will not execute or even download JavaScript files.

You would have to use something like FireBug to get the URL for the data being pulled in via JavaScript, and point your HttpWebRequest at that.

回答6:

Use HttpWebRequest to download the page. Search the source code for the relevant AJAX information and then use a new HttpWebRequest to pull that data down.

回答7:

You could use of the PhantomJs. I had this Issue, but don't found solution for my problem. In my opinion, best solution is This.

My solution is look like this:

var page = require('webpage').create();

page.open("https://sample.com", function(){
    page.evaluate(function(){
        var i = 0,
        oJson = jsonData,
        sKey;
        localStorage.clear();

        for (; sKey = Object.keys(oJson)[i]; i++) {
            localStorage.setItem(sKey,oJson[sKey])
        }
    });

    page.open("https://sample.com", function(){
        setTimeout(function(){
         page.render("screenshoot.png") 
            // Where you want to save it    
           console.log(page.content); //page source
            // You can access its content using jQuery
            var fbcomments = page.evaluate(function(){
                return $("body").contents().find(".content") 
            }) 
            phantom.exit();
        },10000)
    });     
});