Import an HTML File into the Rich Text Editor or Export a Document to HTML
- 7 minutes to read
The Rich Text Editor allows you to import HTML files and save documents as HTML. When you open an HTML file, the control 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. However, we must emphasize that the Rich Text Editor is not an HTML editor/browser. It can display your HTML document differently from your web browser even if all HTML tags were imported into the control’s document model.
Import HTML Content
Load an HTML Page
Use the RichEditControl.LoadDocument or RichEditControl.Document.LoadDocument method to import an HTML page into the Rich Text Editor.
The sourceUri parameter of the LoadDocument method allows you to load files associated with an HTML document.
richEditControl1.LoadDocument("HtmlDocument.html", DocumentFormat.Html, "HtmlDocument_files");
Specify HTML Text
Assign HTML text to the RichEditControl.HtmlText or RichEditControl.Document.HtmlText property.
using DevExpress.XtraRichEdit.API.Native;
using System.Net;
// ...
using (var client = new WebClient())
{
string html = client.DownloadString("https://docs.devexpress.com/WindowsForms/9610/");
richEditControl1.HtmlText = html;
}
You can also use the following methods to insert HTML text into the document:
Define Import Options
Handle the RichEditControl.BeforeImport event and use the HtmlDocumentImporterOptions class properties to specify import options for HTML documents. These options are also returned by the RichEditControl.Options.Import.Html property.
using DevExpress.XtraRichEdit.API.Native;
using DevExpress.XtraRichEdit;
using DevExpress.XtraRichEdit.Import;
using System.Text;
// ...
richEditControl1.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 to the Rich Text Editor, you can export the document to a different format.
Example 1. Convert HTML to PDF
Use the RichEditControl.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;
// ...
Document document = richEditControl1.Document;
// Load an HTML document.
document.LoadDocument("HtmlDocument.html", DocumentFormat.Html);
// 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.
richEditControl1.ExportToPdf("PdfDocument.pdf", options);
Example 2. Convert HTML to DOCX
using DevExpress.XtraRichEdit.API.Native;
using DevExpress.XtraRichEdit;
// ...
Document document = richEditControl1.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
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.
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:
If you import an HTML file that contains tables and these tables extend into page margins, disable the following option: RichEditControl.Document.CompatibilitySettings.AllowTablesOutstepMargins.
The HTML document is loaded in CompatibilityMode.ModeNotSpecified mode. In this case, the RichEdit Control uses the compatibility settings of previous Microsoft Word versions. Set the CompatibilitySettings.CompatibilityMode property to CompatibilityMode.Mode15 after the document is loaded to enable compatibility with the latest Microsoft Word version and process the document correctly:
RichEditControlimports paragraphs from an HTML document with line spacing between paragraphs (i.e. the SpacingBefore and SpacingAfter properties are set to12 pt). Change the value of these properties before import to remove line spacing.
Export to HTML
Save as HTML File
Use the RichEditControl.SaveDocument method to export a document to HTML.
// Load a document.
richEditControl1.LoadDocument("Document.docx");
// Export the document to a file in HTML format.
richEditControl1.SaveDocument("HtmlDocument.html", DocumentFormat.Html);
// Export the document to a file stream in HTML format.
using (FileStream fileStream = new FileStream("HtmlDocument2.html", FileMode.Create)) {
richEditControl1.SaveDocument(fileStream, DocumentFormat.Html);
}
Return HTML Text
Use the RichEditControl.Document.HtmlText property or SubDocument.GetHtmlText method to convert document content to HTML.
// Load a document.
richEditControl1.LoadDocument("Document.docx");
// Export the document to a file in HTML format.
System.IO.File.WriteAllText("HtmlDocument.html", richEditControl1.Document.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:
Handle the RichEditControl.BeforeExport event;
Pass an HtmlDocumentExporterOptions instance to the SubDocument.GetHtmlText method;
Use the RichEditControl.Options.Export.Html property.
using DevExpress.XtraRichEdit.API.Native;
using DevExpress.XtraRichEdit;
using DevExpress.XtraRichEdit.Export;
// ...
richEditControl1.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;
}
};
Export Images
Embed Images
Enable the HtmlDocumentExporterOptions.EmbedImages option to embed images in an HTML file as Base64-encoded data.
Specify External Image Location
Method 1
Use the HtmlDocumentExporterOptions.UriExportType and HtmlDocumentExporterOptions.TargetUri properties to specify a location for external images.
Method 2
Implement and register a custom IUriProvider. This interface contains the CreateImageUri and CreateCssUri methods that allow you to specify locations for external images and styles.