Edit HTML and Markdown Documents in C#

Document Editing APIs for C# Applications

Aspose.HTML for .NET provides structured APIs for editing HTML and Markdown content. Use an HTMLDocument to change an HTML DOM, or parse Markdown into a typed syntax tree before updating its nodes. After editing, save the document in its editable format or pass it to a separate archive or conversion workflow.

Choose an HTML or Markdown Editing Workflow

• HTML Editor . Load an HTML file, URL, string, or stream; locate DOM elements; change text, attributes, styles, or document structure; and save the modified HTML.
• Markdown Editor . Parse an existing MD file into a typed AST, update headings, paragraphs, lists, links, or other syntax nodes, and serialize the modified tree back to Markdown.
• HTML to MHTML Workflow . Edit HTML first, then package the changed document and handled resources as an MHTML archive. Existing MHTML and MHT archives are rendering or conversion inputs rather than editable HTML DOM sources.

Update HTML Page Metadata in C#

This example loads an HTML document, updates its page title and meta description, creates missing metadata elements when necessary, and saves the edited file. The Markdown workflow uses a separate typed syntax-tree API.

using Aspose.Html;
using Aspose.Html.Dom;

using HTMLDocument document = new HTMLDocument("input.html");

// Update the document title through the HTMLDocument API
document.Title = "Updated page title";

// Find the head and create the description element when it is missing
Element head = document.QuerySelector("head");
if (head != null)
{
    Element description = document.QuerySelector("meta[name='description']");
    if (description == null)
    {
        description = document.CreateElement("meta");
        description.SetAttribute("name", "description");
        head.AppendChild(description);
    }

    description.SetAttribute("content", "Updated page description.");
}

document.Save("edited.html");

Core HTML Editing Steps

1. Load the source with an HTMLDocument constructor.
2. Locate the required element with QuerySelector() , GetElementById(), XPath, or another DOM navigation method.
3. Update text, attributes, styles, or child nodes through the DOM API.
4. Call Save() to write HTML, or continue to a dedicated conversion or MHTML archive workflow.

What You Can Edit Programmatically

• Document structure. Add, replace, move, or remove HTML DOM nodes and supported Markdown syntax nodes.
• Text and markup. Update plain text, HTML markup, headings, paragraphs, lists, links, code blocks, and other structured content.
• HTML attributes and CSS. Change element attributes, inline styles, <style> content, and stylesheet references.
• Selected nodes. Find HTML elements with CSS selectors or XPath queries , and traverse Markdown through typed AST nodes.
• Output workflow. Save editable HTML or Markdown, create MHTML from edited HTML, or send the prepared content to a conversion API when the final result must be PDF, DOCX, XPS, or an image.

Document Editing Documentation

The Edit HTML Document guide covers DOM nodes, attributes, text, and markup changes. Use Edit and Modify Markdown for typed Markdown AST examples. The Working with HTML Documents section explains loading, editing, environment configuration, saving, and resource handling.

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.

HTML, Markdown, and MHTML Editing FAQ

1. How do I edit an HTML file in C#?

Load the file into an HTMLDocument, find the required DOM elements with QuerySelector(), GetElementById(), XPath, or DOM traversal, update their text, attributes, styles, or child nodes, and call Save() to write the edited HTML.

2. Should I edit Markdown directly or convert it to HTML first?

Edit the MarkdownSyntaxTree directly when the result must remain an MD file. Convert Markdown to HTML first when the workflow requires HTML DOM operations, browser-oriented markup, or a rendered output rather than updated Markdown source.

3. Can I edit an existing MHTML file in C#?

An existing MHTML or MHT archive is not loaded as an editable HTMLDocument. Edit the original HTML and create a new MHTML archive from the updated document; use the conversion workflow when only the archived MHTML source is available.