Visual FoxPro

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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LOCAL loEmail
LOCAL lcCid
LOCAL loSbHtml
LOCAL lnNumReplaced

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

loEmail = CreateObject('Chilkat.Email')
loEmail.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.
lcCid = loEmail.AddRelatedString("styles.css","body { color: black; }","utf-8")
IF (loEmail.LastMethodSuccess = 0) THEN
    ? loEmail.LastErrorText
    RELEASE loEmail
    CANCEL
ENDIF

*  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.
loSbHtml = CreateObject('Chilkat.StringBuilder')
loSbHtml.Append('<html><head><link rel="stylesheet" href="cid:PLACEHOLDER_CID"/></head><body>Styled content.</body></html>')
lnNumReplaced = loSbHtml.Replace("PLACEHOLDER_CID",lcCid)
loEmail.SetHtmlBody(loSbHtml.GetAsString())

*  Add a custom header field to the first related item (index 0).
loEmail.AddRelatedHeader(0,"X-Custom-Related-Header","some value")

*  The custom header now appears in the related item's MIME part.
? loEmail.GetMime()

RELEASE loEmail
RELEASE loSbHtml