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Use Word Processing Document API to Load HTML Files or Export Documents to HTML

  • 6 minutes to read

The Word Processing Document API allows you to import HTML files and save documents as HTML. When you open an HTML file, the RichEditDocumentServer converts HTML content into its internal document model. Some HTML tags and CSS attributes have no counterparts in Open XML and RTF formats. You can find more information about supported and unsupported HTML tags in the following help topic: HTML Support Limitations.

Import HTML Content

Load an HTML Page

Use the RichEditDocumentServer.LoadDocument or RichEditDocumentServer.Document.LoadDocument method to load an HTML page.

using (var wordProcessor = new RichEditDocumentServer())
{
    wordProcessor.LoadDocument("HtmlDocument.html", DocumentFormat.Html);
}

The sourceUri parameter of the LoadDocument method allows you to load files associated with an HTML document.

using (var wordProcessor = new RichEditDocumentServer())
{
    wordProcessor.LoadDocument("HtmlDocument.html", DocumentFormat.Html, "HtmlDocument_files");
}

Specify HTML Text

Assign HTML text to the RichEditDocumentServer.HtmlText or RichEditDocumentServer.Document.HtmlText property.

using DevExpress.XtraRichEdit.API.Native;
using System.Net;
// ...

using (var wordProcessor = new RichEditDocumentServer())
{
    using (var client = new WebClient())
    {
        string html = client.DownloadString("https://docs.devexpress.com/WindowsForms/9610/");
        wordProcessor.HtmlText = html;
    }
}

You can also use the following methods to insert HTML text into the document:

Define Import Options

Handle the RichEditDocumentServer.BeforeImport event and use the HtmlDocumentImporterOptions class properties to specify import options for HTML documents. These options are also returned by the RichEditDocumentServer.Options.Import.Html property.

using DevExpress.XtraRichEdit;
using DevExpress.XtraRichEdit.Import;
using System.Text;
// ...

wordProcessor.BeforeImport += (s, e) =>
{
    if (e.DocumentFormat == DocumentFormat.Html)
    {
        var options = (HtmlDocumentImporterOptions)e.Options;
        // Specify encoding.
        options.AutoDetectEncoding = false;
        options.Encoding = Encoding.UTF8;
        // Skip media rules.
        options.IgnoreMediaQueries = true;
        // Load images synchronously with HTML documents.
        options.AsyncImageLoading = false;
        // Preserve image resolution.
        options.ImageScalingDpi = 96;
    }
};

Convert HTML To Another Format

After you load an HTML file, you can export the document to a different format.

Example 1. Convert HTML to PDF

Use the RichEditDocumentServer.ExportToPdf method to export HTML content to PDF. Pass a PdfExportOptions instance to the method to specify export options.

using DevExpress.XtraRichEdit.API.Native;
using DevExpress.XtraRichEdit;
// ...

using (var wordProcessor = new RichEditDocumentServer())
{
    // Load an HTML document.
    wordProcessor.LoadDocument("HtmlDocument.html", DocumentFormat.Html);
    Document document = wordProcessor.Document;

    // Define PDF export options.
    var options = new DevExpress.XtraPrinting.PdfExportOptions();
    options.ConvertImagesToJpeg = false;
    options.ImageQuality = DevExpress.XtraPrinting.PdfJpegImageQuality.Highest;

    // Specify page settings before export to PDF.
    document.Unit = DevExpress.Office.DocumentUnit.Inch;
    // Set page size.
    document.Sections[0].Page.Width = 8.5f;
    document.Sections[0].Page.Height = 11f;
    // Change margin settings.
    document.Sections[0].Margins.Top = 0;
    document.Sections[0].Margins.Bottom = 0;
    document.Sections[0].Margins.Left = 0.2f;
    document.Sections[0].Margins.Right = 0.2f;

    // Export the document to PDF.
    wordProcessor.ExportToPdf("PdfDocument.pdf", options);
}

Example 2. Convert HTML to DOCX

using DevExpress.XtraRichEdit.API.Native;
using DevExpress.XtraRichEdit;
// ...

using (var wordProcessor = new RichEditDocumentServer())
{
    Document document = wordProcessor.Document;
    // Load an HTML document.
    document.LoadDocument("HtmlDocument.html", DocumentFormat.Html);

    // Modify and format the document.
    // ...

    // Save the document as DOCX.
    document.SaveDocument("Document.docx", DocumentFormat.OpenXml);
}

Import Tips

  1. Implement and register a custom IUriStreamProvider to specify how to load images from an HTML document. For example, you can use this service when you import an HTML file that contains images referenced with a custom prefix.

    View Example: Import HTML Files that Contain Images with a Custom Prefix

  2. If you import content from an HTTPS website, you may need to specify the security protocol enabled for this site. For example, if the site uses TLS 1.2 protocol, add the following line to your code:

    System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
    
  3. If you import an HTML file that contains tables and these tables extend into page margins, disable the following option: RichEditDocumentServer.Document.CompatibilitySettings.AllowTablesOutstepMargins.

Export to HTML

Save as HTML File

Use the RichEditDocumentServer.SaveDocument method to export a document to HTML.

using (var wordProcessor = new RichEditDocumentServer())
{
    // Load a document.
    wordProcessor.LoadDocument("Document.docx");
    // Export the document to a file in HTML format.
    wordProcessor.SaveDocument("HtmlDocument.html", DocumentFormat.Html);
    // Export the document to a file stream in HTML format.
    using (FileStream fileStream = new FileStream("HtmlDocument2.html", FileMode.Create))
    {
        wordProcessor.SaveDocument(fileStream, DocumentFormat.Html);
    }
}

Return HTML Text

Use the RichEditDocumentServer.HtmlText property or SubDocument.GetHtmlText method to convert document content to HTML.

using (var wordProcessor = new RichEditDocumentServer())
{
    // Load a document.
    wordProcessor.LoadDocument("Document.docx");
    // Export the document to a file in HTML format.
    System.IO.File.WriteAllText("HtmlDocument.html", wordProcessor.HtmlText);
}

Define Export Options

The HtmlDocumentExporterOptions class contains options used to export a document to HTML. You can use one of the following methods to specify these options:

using DevExpress.XtraRichEdit;
using DevExpress.XtraRichEdit.Export;
// ...

wordProcessor.BeforeExport += (s, e) =>
{
    if (e.DocumentFormat == DocumentFormat.Html)
    {
        var options = (HtmlDocumentExporterOptions)e.Options;
        // Embed images in HTML pages.
        options.EmbedImages = true;
        // Specify how to export style sheets.
        options.CssPropertiesExportType = DevExpress.XtraRichEdit.Export.Html.CssPropertiesExportType.Style;
        // Specify the root tag for export.
        options.ExportRootTag = DevExpress.XtraRichEdit.Export.Html.ExportRootTag.Body;
    }
};
See Also