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AngleSharp

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3 Jul 2013BSD28 min read 260.5K   4.3K   166  
Bringing the DOM to C# with a HTML5/CSS3 parser written in C#.
using AngleSharp;
using AngleSharp.DOM.Html;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace Samples.ViewModels
{
    public abstract class RequestViewModel : BaseViewModel
    {
        #region Members

        Task current;
        CancellationTokenSource cts;
        String status;
        Int32 state;

        #endregion

        #region Static members

        static Uri recentUrl;
        static String recentAddress;
        static Int32 recentState;
        static HTMLDocument recentDocument;

        #endregion

        #region Properties

        public String Address
        {
            get { return recentAddress; }
        }

        public String Status
        {
            get { return status; }
            set
            {
                status = value;
                RaisePropertyChanged();
            }
        }

        #endregion

        #region Methods

        public void Load(String url)
        {
            if (current != null && !current.IsCompleted)
                cts.Cancel(false);

            cts = new CancellationTokenSource();
            current = LoadAsync(url, cts.Token);
        }

        public Boolean DisplayRecent()
        {
            if (recentState != state && SettingsViewModel.Instance.IsInSharedDocumentMode)
            {
                if (current != null && !current.IsCompleted)
                    cts.Cancel(false);

                cts = new CancellationTokenSource();
                current = Use(recentUrl, recentDocument, cts.Token);
                state = recentState;
                Status = "Displaying: " + recentUrl;
                return true;
            }

            return false;
        }

        async Task LoadAsync(String url, CancellationToken cancel)
        {
            Stream response;
            var http = new HttpClient();
            var uri = Sanitize(url);
            Status = "Loading " + uri.AbsoluteUri + " ...";

            if (uri.Scheme.Equals("file", StringComparison.Ordinal))
                response = File.Open(uri.AbsolutePath.Substring(1), FileMode.Open);
            else
            {
                var request = await http.GetAsync(uri, cancel);
                response = await request.Content.ReadAsStreamAsync();
                cancel.ThrowIfCancellationRequested();
            }

            Status = "Parsing " + uri.AbsoluteUri + " ...";
            var document = DocumentBuilder.Html(response);
            response.Close();

            cancel.ThrowIfCancellationRequested();
            await Use(uri, document, cancel);

            UpdateRecent(document, url, uri);
            Status = "Displaying: " + url;
        }

        void UpdateRecent(HTMLDocument document, String url, Uri uri)
        {
            recentAddress = url;
            SettingsViewModel.Instance.AddUrl(url);
            recentDocument = document;
            recentUrl = uri;
            recentState++;
            state = recentState;
        }

        protected abstract Task Use(Uri url, HTMLDocument document, CancellationToken cancel);

        #endregion
    }
}

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License

This article, along with any associated source code and files, is licensed under The BSD License


Written By
Chief Technology Officer
Germany Germany
Florian lives in Munich, Germany. He started his programming career with Perl. After programming C/C++ for some years he discovered his favorite programming language C#. He did work at Siemens as a programmer until he decided to study Physics.

During his studies he worked as an IT consultant for various companies. After graduating with a PhD in theoretical particle Physics he is working as a senior technical consultant in the field of home automation and IoT.

Florian has been giving lectures in C#, HTML5 with CSS3 and JavaScript, software design, and other topics. He is regularly giving talks at user groups, conferences, and companies. He is actively contributing to open-source projects. Florian is the maintainer of AngleSharp, a completely managed browser engine.

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