Validate WCAG Accessibility Rules in C#

Select Web Accessibility Rules with a .NET API

Aspose.HTML for .NET provides an AccessibilityRules repository containing WCAG 2.0 principles, guidelines, success criteria, and techniques. Select the required rules by code, create an AccessibilityValidator, and check an HTML file or webpage for related accessibility issues.

Selecting specific rules is useful when a project follows a defined accessibility policy or needs to test one type of issue. The validation report shows which checks failed and which HTML elements require attention.

Check HTML Against Selected WCAG Rules

The example selects four HTML techniques covering image alternatives, form labels, iframe titles, and unique element IDs. GetRules() returns the matching IRule objects, which are then passed to a focused validator.

using System;
using System.Collections.Generic;
using System.IO;
using Aspose.Html;
using Aspose.Html.Accessibility;
using Aspose.Html.Accessibility.Results;

string documentPath = Path.Combine("data", "input.html");
string[] ruleCodes = { "H37", "H44", "H64", "H93" };

WebAccessibility webAccessibility = new WebAccessibility();

// Retrieve only the requested accessibility rules
IList<IRule> selectedRules = webAccessibility.Rules.GetRules(ruleCodes);
AccessibilityValidator validator = webAccessibility.CreateValidator(
    selectedRules,
    ValidationBuilder.All);

// Validate the document against the selected rules
using HTMLDocument document = new HTMLDocument(documentPath);
ValidationResult validationResult = validator.Validate(document);

if (!validationResult.Success)
{
    Console.WriteLine(validationResult.SaveToString());
}

How to Validate Specific Accessibility Rules

1. Create a WebAccessibility object and access its Rules repository.
2. Define the codes for the principles, guidelines, criteria, or techniques required by the project’s validation policy.
3. Pass the codes to GetRules() and verify that every requested rule was returned.
4. Create an AccessibilityValidator from the resulting IList<IRule>.
5. Load the HTML with HTMLDocument , call Validate(), and inspect or save the returned report.

Understand the Accessibility Rule Hierarchy

• Principles. Top-level WCAG categories describe the broad goals of accessible content.
• Guidelines. Each principle contains guidelines that organize related accessibility requirements.
• Success criteria. Criteria provide testable requirements and identify conformance levels A, AA, or AAA.
• Techniques and failures. Technique codes such as H37 describe implementation checks; failure codes identify patterns that violate a criterion.
• Code-based selection. GetRules() accepts one or more codes and omits codes that are not present in the repository.
• Focused validation. Selected rules can support project-specific checks, but a narrow rule list is not a complete accessibility audit.

Use the HTML Accessibility Validator when the application needs a broad or builder-filtered check instead of an explicit list of rule codes.

WCAG Rules Documentation and Reference

Read Web Accessibility Rules for the full repository hierarchy and examples of GetPrinciple(), GetGuideline(), GetCriterion(), and GetRules(). The W3C WCAG Techniques index describes the purpose and test procedure for individual technique and failure codes.

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.

Web Accessibility Rules FAQ

1. What is the difference between a WCAG criterion and a technique?

A success criterion is a testable requirement used to determine WCAG conformance. A technique describes one documented way to meet a criterion, while a failure describes a pattern that does not meet it. Passing one technique does not by itself establish conformance.

2. How do I validate only specific WCAG rules in C#?

Pass the required codes to AccessibilityRules.GetRules(), create an AccessibilityValidator with the returned IList<IRule>, and validate the HTMLDocument. This limits the report to the selected rule scope and applicable builder settings.

3. Can GetRules() accept principles, guidelines, criteria, and techniques?

Yes. Each of these rule types implements IRule, so their codes can be supplied to GetRules(). Choose the level that matches the intended scope; a higher-level object includes a broader group, while a technique code targets a specific check.

4. What happens if a requested accessibility rule code is not found?

The GetRules() method omits a code that is not present in the repository. Compare the returned collection with the requested codes before validation so a spelling error or unsupported code does not silently reduce the intended coverage.

5. Does validating selected rules prove WCAG compliance?

No. It proves only that the document was evaluated against the selected automated checks. WCAG conformance requires the applicable success criteria to be assessed, including requirements that need manual testing and human judgment.