CSS Selector Tester Online and C# Queries

Test CSS Selectors Online

Use the CSS Selector Tester to find elements on a public webpage by CSS selector. Enter a URL and a selector such as article h2, .product-card, or a[href]. The tool displays the matching HTML elements and generates C# code for the same query.

1. Enter the URL of the webpage you want to inspect.
2. Enter a CSS selector that identifies the required elements.
3. Click Find, review the matches, and copy the result or generated C# code.

Select HTML Elements with a CSS Selector in C#

Aspose.HTML for .NET exposes standard selector methods through the HTML DOM. This example loads the URL currently shown in the widget and uses QuerySelectorAll() to return every match as a NodeList. Change the URL or selector in the widget and this server-rendered C# example updates automatically. Use QuerySelector() when only the first matching element is required.

using System;
using Aspose.Html;
using Aspose.Html.Collections;
using Aspose.Html.Dom;

// Create an HTML document
string url = "https://www.aspose.com/";
using HTMLDocument document = new HTMLDocument(url);

// Select the matching HTML elements
NodeList elements = document.QuerySelectorAll("a");

foreach (Element element in elements)
{
    // Print the element markup
    Console.WriteLine(element.OuterHTML);
}

Common CSS Selector Patterns

CSS selectors locate elements by name, ID, class, attribute, position, or DOM relationship:

• p matches every <p> element.
• #summary matches the element whose id is summary.
• .notice matches elements with the notice class.
• a[href] matches links that have an href attribute.
• article > p matches <p> elements that are direct children of an <article>.
• h1, h2 matches elements selected by either expression.

CSS selectors do not provide a general condition for matching visible text. When the query must test text content, move through ancestors, or apply more complex predicates, use the XPath Tester .

CSS Selector API Workflow in C#

1. Create an HTMLDocument from a local HTML file or URL.
2. Define a selector that matches the required elements.
3. Call QuerySelector() for one element or QuerySelectorAll() for all matches.
4. Read properties such as TextContent, InnerHTML, or OuterHTML, or update the selected DOM elements.

Selection alone does not modify the source document. If you change returned elements and need to keep the result, save the updated HTMLDocument explicitly.

CSS Selector Documentation and API Reference

Use these resources for selector syntax, DOM navigation, and production C# examples:

• How to Use CSS Selectors in C# explains QuerySelector() and QuerySelectorAll() with practical examples.
• CSS Selector Types and Syntax covers type, class, ID, attribute, combinator, and pseudo-class selectors.
• HTML Navigation in C# compares direct DOM traversal, CSS selectors, and XPath queries.

Get Started with Aspose.HTML for .NET API

Install Aspose.HTML for .NET from NuGet with the .NET CLI:

dotnet add package Aspose.HTML

You can also use the NuGet Package Manager UI or run Install-Package Aspose.HTML in the Package Manager Console. See the installation guide for setup details, or request a temporary license to evaluate the API without evaluation limitations.

FAQ

1. What is a CSS selector?

A CSS selector is a pattern that identifies HTML elements by tag name, ID, class, attribute, position, or relationship to other elements. Browsers and DOM APIs use the same selector syntax for styling and element lookup.

2. What is the difference between QuerySelector() and QuerySelectorAll()?

The QuerySelector() method returns the first matching element or null. The QuerySelectorAll() method returns a NodeList containing every matching element; the list is empty when nothing matches.

3. Can a CSS selector find an element by its text?

Standard CSS selectors do not provide a general text-content condition. Select candidate elements and inspect TextContent in C#, or use XPath when the expression itself must match text.

4. Why does my CSS selector return no matches?

Check the selector syntax, class and ID spelling, attribute values, and parent-child relationships against the loaded HTML. A space selects descendants, while > selects only direct children.