Popularity
2.6
Growing
Activity
5.2
-
117
6
5

Description

LtGt is a minimalistic library for working with HTML. It can parse any HTML5-compliant code into an object model which you can use to traverse nodes or locate specific elements. The library establishes itself as a foundation that you can build upon, and comes with a lot of extension methods that can help navigate the DOM easily. It also supports HTML rendering, so you can turn any HTML object tree to code.

Programming language: C#
Tags: Linq     HTML     Parse     CSS     Markup     HTML and CSS    
Latest version: v2.1

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README

LtGt

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Project status: maintenance mode (bug fixes only).

LtGt is a minimalistic library for working with HTML. It can parse any HTML5-compliant code into an object model which you can use to traverse nodes or locate specific elements. The library establishes itself as a foundation that you can build upon, and comes with a lot of extension methods that can help navigate the DOM easily.

This project mostly serves an educational purpose. For real-life performance-critical applications I recommend using AngleSharp instead.

Download

  • NuGet: dotnet add package LtGt

Features

  • Parse any HTML5-compliant code
  • Traverse the DOM using LINQ or Seq
  • Use basic element selectors like GetElementById(), GetElementsByTagName(), etc
  • Use CSS selectors via QueryElements()
  • Convert any HTML node to its equivalent Linq2Xml representation
  • Render any HTML entity to code
  • Targets .NET Framework 4.5+ and .NET Standard 1.6+

Screenshots

[dom](.screenshots/dom.png) [css selectors](.screenshots/css-selectors.png)

Usage

LtGt is a library written in F# but it provides two separate idiomatic APIs that you can use from both C# and F#.

Parse a document

C#

using LtGt;

const string html = @"<!doctype html>
<html>
  <head>
    <title>Document</title>
  </head>
  <body>
    <div>Content</div>
  </body>
</html>";

// This throws an exception on parse errors
var document = Html.ParseDocument(html);

// -or-

// This returns a wrapped result instead
var documentResult = Html.TryParseDocument(html);
if (documentResult.IsOk)
{
    // Handle result
    var document = documentResult.ResultValue;
}
else
{
    // Handle error
    var error = documentResult.ErrorValue;
}

F#

open LtGt

let html = "<!doctype html>
<html>
  <head>
    <title>Document</title>
  </head>
  <body>
    <div>Content</div>
  </body>
</html>"

// This throws an exception on parse errors
let document = Html.parseDocument html

// -or-

// This returns a wrapped result instead
match Html.tryParseDocument html with
| Result.Ok document -> // handle result
| Result.Error error -> // handle error

Parse a fragment

C#

const string html = "<div id=\"some-element\"><a href=\"https://example.com\">Link</a></div>";

// Parse an element node
var element = Html.ParseElement(html);

// Parse any node
var node = Html.ParseNode(html);

F#

let html = "<div id=\"some-element\"><a href=\"https://example.com\">Link</a></div>"

// Parse an element node
let element = Html.parseElement html

// Parse any node
let node = Html.parseNode html

Find specific element

C#

var element1 = document.GetElementById("menu-bar");
var element2 = document.GetElementsByTagName("div").FirstOrDefault();
var element3 = document.GetElementsByClassName("floating-button floating-button--enabled").FirstOrDefault();

var element1Data = element1.GetAttributeValue("data");
var element2Id = element2.GetId();
var element3Text = element3.GetInnerText();

F#

let element1 = document |> Html.tryElementById "menu-bar"
let element2 = document |> Html.elementsByTagName "div" |> Seq.tryHead
let element3 = document |> Html.elementsByClassName "floating-button floating-button--enabled" |> Seq.tryHead

let element1Data = element1 |> Option.bind (Html.tryAttributeValue "data")
let element2Id = element2 |> Option.bind Html.tryId
let element3Text = element3 |> Option.map Html.innerText

You can leverage the full power of CSS selectors as well.

C#

var element = document.QueryElements("div#main > span.container:empty").FirstOrDefault();

F#

let element = document |> CssSelector.queryElements "div#main > span.container:empty" |> Seq.tryHead

Check equality

You can compare two HTML entities by value, including their descendants.

C#

var element1 = new HtmlElement("span",
    new HtmlAttribute("id", "foo"),
    new HtmlText("bar"));

var element2 = new HtmlElement("span",
    new HtmlAttribute("id", "foo"),
    new HtmlText("bar"));

var element3 = new HtmlElement("span",
    new HtmlAttribute("id", "foo"),
    new HtmlText("oof"));

var firstTwoEqual = HtmlEntityEqualityComparer.Instance.Equals(element1, element2); // true
var lastTwoEqual = HtmlEntityEqualityComparer.Instance.Equals(element2, element3); // false

F#

let element1 = HtmlElement("span",
    HtmlAttribute("id", "foo"),
    HtmlText("bar"))

let element2 = HtmlElement("span",
    HtmlAttribute("id", "foo"),
    HtmlText("bar"))

let element3 = HtmlElement("span",
    HtmlAttribute("id", "foo"),
    HtmlText("oof"))

let firstTwoEqual = Html.equal element1 element2 // true
let lastTwoEqual = Html.equal element2 element3 // false

Convert to Linq2Xml

You can convert LtGt's objects to System.Xml.Linq objects (XNode, XElement, etc). This can be useful if you need to convert HTML to XML or if you want to use XPath to select nodes.

C#

var htmlDocument = Html.ParseDocument(html);
var xmlDocument = (XDocument) htmlDocument.ToXObject();
var elements = xmlDocument.XPathSelectElements("//input[@type=\"submit\"]");

F#

let htmlDocument = Html.parseDocument html
let xmlDocument = htmlDocument |> Html.toXObject :?> XDocument
let elements = xmlDocument.XPathSelectElements("//input[@type=\"submit\"]")

Render nodes

You can turn any entity to its equivalent HTML code.

C#

var element = new HtmlElement("div",
    new HtmlAttribute("id", "main"),
    new HtmlText("Hello world"));

var html = element.ToHtml(); // <div id="main">Hello world</div>

F#

let element = HtmlElement("div",
    HtmlAttribute("id", "main"),
    HtmlText("Hello world"))

let html = element |> Html.toHtml // <div id="main">Hello world</div>

Benchmarks

This is how LtGt compares to popular HTML libraries when it comes to parsing a document (in this case, a YouTube video watch page). The results are not in favor of LtGt so if performance is important for your task, you should probably consider using a different parser. That said, these results are still pretty impressive for a parser built with parser combinators as opposed to a traditional manual approach.

BenchmarkDotNet=v0.12.0, OS=Windows 10.0.14393.3384 (1607/AnniversaryUpdate/Redstone1)
Intel Core i5-4460 CPU 3.20GHz (Haswell), 1 CPU, 4 logical and 4 physical cores
Frequency=3125000 Hz, Resolution=320.0000 ns, Timer=TSC
.NET Core SDK=3.1.100
[Host]     : .NET Core 3.1.0 (CoreCLR 4.700.19.56402, CoreFX 4.700.19.56404), X64 RyuJIT DEBUG
DefaultJob : .NET Core 3.1.0 (CoreCLR 4.700.19.56402, CoreFX 4.700.19.56404), X64 RyuJIT
Method Mean Error StdDev Ratio Rank
AngleSharp 11.94 ms 0.104 ms 0.097 ms 0.29 1
HtmlAgilityPack 20.51 ms 0.140 ms 0.124 ms 0.49 2
LtGt 41.59 ms 0.450 ms 0.399 ms 1.00 3