Dart

Add a Related String Resource to an Email

Demonstrates the Chilkat Email.AddRelatedString method, which adds a text-based related MIME resource, such as a style sheet, from an in-memory string and returns the generated Content-ID. The first argument is the MIME resource name, the second is the text content, and the third is the charset used to encode it. Because the Content-ID is generated by the call, this example adds the style sheet first, then builds an HTML body in a StringBuilder that references the style sheet by that cid:, and passes the result to SetHtmlBody.

Background: Related items are not always images loaded from disk — sometimes the resource is text you already have in memory, like a generated CSS style sheet or an SVG. AddRelatedString lets you embed such content directly without writing a temporary file first. As with other related items, it lives in the multipart/related enclosure and is referenced from the HTML by the Content-ID the method returns.

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Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // Demonstrates the AddRelatedString method, which adds a text-based related MIME resource
  // (such as a style sheet) from an in-memory string and returns the generated Content-ID.
  // The first argument is the resource name, the second is the text content, the third is the charset.

  final email = CkEmail();
  email.subject = 'Email with a related style sheet';

  // Add the text-based related resource first; capture the generated Content-ID.
  final String cid;
  try {
    cid = email.addRelatedString('styles.css', 'body { color: navy; }', 'utf-8');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Build the HTML body, referencing the related style sheet by its Content-ID.  A
  // placeholder is used and then replaced with the actual Content-ID.
  final sbHtml = CkStringBuilder();
  sbHtml.append('<html><head><link rel="stylesheet" href="cid:PLACEHOLDER_CID"/></head><body>Styled content.</body></html>');
  final numReplaced = sbHtml.replace('PLACEHOLDER_CID', cid);
  email.setHtmlBody(sbHtml.getAsString());

  print('Related Content-ID = $cid');
  print('NumRelatedItems = ${email.numRelatedItems}');
}