Count the Related Items in an Email

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Demonstrates the read-only Chilkat Email.NumRelatedItems property, which is the number of related MIME items in the email. Related items are resources — such as images or style sheets — embedded with an HTML body in a multipart/related enclosure, and are commonly referenced by the HTML using a cid: URL or a Content-Location. Indexes are zero-based. This example sets an HTML body, adds a related item, and prints the count.

Background: When an HTML email shows an image that travels inside the message (rather than being downloaded from the web), the image is a "related item." The HTML references it with <img src="cid:logo.png">, and a matching part carries a Content-ID of logo.png. The whole bundle lives in a multipart/related enclosure. This is different from an attachment: related items are meant to be displayed as part of the body, not saved as separate files.

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//  Demonstrates the read-only Email.NumRelatedItems property.  Related items are
//  resources (such as images or style sheets) embedded alongside an HTML body in a
//  multipart/related enclosure, typically referenced from the HTML by a cid: URL.

Chilkat.Email email = new Chilkat.Email();

//  Set an HTML body that references a related item by content-id.
email.SetHtmlBody("<html><body><img src=\"cid:logo.png\"/></body></html>");

//  Add the related item.  AddRelatedString returns the content-id assigned to it.
//  The empty charset argument means no charset conversion is applied.
string cid = email.AddRelatedString("logo.png","(pretend this is image data)","");
Debug.WriteLine("Related content-id = " + cid);

Debug.WriteLine("NumRelatedItems = " + Convert.ToString(email.NumRelatedItems));