Add a Related String Resource to an Email

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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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    //  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.

    email := chilkat.NewEmail()
    email.SetSubject("Email with a related style sheet")

    //  Add the text-based related resource first; capture the generated Content-ID.
    cid := email.AddRelatedString("styles.css","body { color: navy; }","utf-8")
    if email.LastMethodSuccess() == false {
        fmt.Println(email.LastErrorText())
        email.DisposeEmail()
        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.
    sbHtml := chilkat.NewStringBuilder()
    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())

    fmt.Println("Related Content-ID = ", *cid)
    fmt.Println("NumRelatedItems = ", email.NumRelatedItems())

    email.DisposeEmail()
    sbHtml.DisposeStringBuilder()