Using CefSharp.Offscreen to retrieve a web page that requires Javascript to render

Question

I have what is hopefully a simple task, but it\'s going to take someone that\'s versed in CefSharp to solve it.

I have an url that I want to retrieve the HTML from.

Answer 1

I know I am doing some archaeology reviving a 2yo post, but a detailed answered may be of use for someone else.

So yes, Cefsharp.Offscreen is fit to the task.

Here under is a class which will handle all the browser activity.

using System;
using System.IO;
using System.Threading;
using CefSharp;
using CefSharp.OffScreen;

namespace [whatever]
{
    public class Browser
    {

        /// 

        /// The browser page
        /// 
        public ChromiumWebBrowser Page { get; private set; }
        /// 

        /// The request context
        /// 
        public RequestContext RequestContext { get; private set; }

        // chromium does not manage timeouts, so we'll implement one
        private ManualResetEvent manualResetEvent = new ManualResetEvent(false);

        public Browser()
        {
            var settings = new CefSettings()
            {
                //By default CefSharp will use an in-memory cache, you need to     specify a Cache Folder to persist data
                CachePath =     Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "CefSharp\\Cache"),
            };

            //Autoshutdown when closing
            CefSharpSettings.ShutdownOnExit = true;

            //Perform dependency check to make sure all relevant resources are in our     output directory.
            Cef.Initialize(settings, performDependencyCheck: true, browserProcessHandler: null);

            RequestContext = new RequestContext();
            Page = new ChromiumWebBrowser("", null, RequestContext);
            PageInitialize();
        }

        /// 

        /// Open the given url
        /// 
        /// the url
        /// 
        public void OpenUrl(string url)
        {
            try
            {
                Page.LoadingStateChanged += PageLoadingStateChanged;
                if (Page.IsBrowserInitialized)
                {
                    Page.Load(url);

                    //create a 60 sec timeout 
                    bool isSignalled = manualResetEvent.WaitOne(TimeSpan.FromSeconds(60));
                    manualResetEvent.Reset();

                    //As the request may actually get an answer, we'll force stop when the timeout is passed
                    if (!isSignalled)
                    {
                        Page.Stop();
                    }
                }
            }
            catch (ObjectDisposedException)
            {
                //happens on the manualResetEvent.Reset(); when a cancelation token has disposed the context
            }
            Page.LoadingStateChanged -= PageLoadingStateChanged;
        }

        /// 

        /// Manage the IsLoading parameter
        /// 
        /// 
        /// 
        private void PageLoadingStateChanged(object sender, LoadingStateChangedEventArgs e)
        {
            // Check to see if loading is complete - this event is called twice, one when loading starts
            // second time when it's finished
            if (!e.IsLoading)
            {
                manualResetEvent.Set();
            }
        }

        /// 

        /// Wait until page initialization
        /// 
        private void PageInitialize()
        {
            SpinWait.SpinUntil(() => Page.IsBrowserInitialized);
        }
    }
}

Now in my app I just need to do the following:

public MainWindow()
{
    InitializeComponent();
    _browser = new Browser();
}

private async void GetGoogleSource()
{
    _browser.OpenUrl("http://icanhazip.com/");
    string source = await _browser.Page.GetSourceAsync();
}

And here is the string I get

"

NotGonnaGiveYouMyIP:)\n

"