Delphi ActiveX

Add a Custom Header to a Related Item

Demonstrates the Chilkat Email.AddRelatedHeader method, which adds a custom MIME header field to an existing related item identified by its zero-based index. This example first adds a related style sheet (which becomes index 0) and captures its generated Content-ID, builds an HTML body that references the style sheet by that cid:, then attaches an extra header field to the related item and prints the resulting MIME.

Background: Like attachments, each related item (an inline image, style sheet, etc.) is a MIME part with its own small header block describing that part — Content-Type, Content-ID, Content-Location, and so on. AddRelatedHeader lets you insert additional fields into that per-part block, which is occasionally required for interoperability with clients that look for specific custom headers on embedded resources.

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var
email: TChilkatEmail;
cid: WideString;
sbHtml: TChilkatStringBuilder;
numReplaced: Integer;

begin
//  Demonstrates the AddRelatedHeader method, which adds a custom MIME header field to an
//  existing related item, identified by its zero-based index.

email := TChilkatEmail.Create(Self);
email.Subject := 'Related item with a custom header';

//  Add a related item first (a style sheet); capture its generated Content-ID.  It becomes
//  related-item index 0.
cid := email.AddRelatedString('styles.css','body { color: black; }','utf-8');
if (email.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(email.LastErrorText);
    Exit;
  end;

//  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.
sbHtml := TChilkatStringBuilder.Create(Self);
sbHtml.Append('<html><head><link rel="stylesheet" href="cid:PLACEHOLDER_CID"/></head><body>Styled content.</body></html>');
numReplaced := sbHtml.Replace('PLACEHOLDER_CID',cid);
email.SetHtmlBody(sbHtml.GetAsString());

//  Add a custom header field to the first related item (index 0).
email.AddRelatedHeader(0,'X-Custom-Related-Header','some value');

//  The custom header now appears in the related item's MIME part.
Memo1.Lines.Add(email.GetMime());