Convert a MIME Entity to multipart/alternative

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Demonstrates the Chilkat Mime.ConvertToMultipartAlt method, which wraps the current entity in a new outer multipart/alternative, making the original the first child. It takes no arguments.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: Use this to add an alternate rendering to an existing message — for example, promoting a plain-text message so an HTML version can be added alongside it. The original content becomes the first (least-preferred) alternative, and you append the richer representation after it. As with the mixed conversion, message-level headers move to the new outer entity.

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bool success = false;

Chilkat.Mime mime = new Chilkat.Mime();
success = mime.LoadMimeFile("qa_data/message.eml");
if (success == false) {
    Debug.WriteLine(mime.LastErrorText);
    return;
}

//  Wrap the current entity in a new outer multipart/alternative entity.  The original entity
//  becomes the first child, ready for an alternate representation to be added.
success = mime.ConvertToMultipartAlt();
if (success == false) {
    Debug.WriteLine(mime.LastErrorText);
    return;
}

//  Add an alternative representation of the same content.
Chilkat.Mime htmlPart = new Chilkat.Mime();
success = htmlPart.SetBodyFromHtml("<html><body>HTML alternative.</body></html>");
if (success == false) {
    Debug.WriteLine(htmlPart.LastErrorText);
    return;
}

success = mime.AppendPart(htmlPart);
if (success == false) {
    Debug.WriteLine(mime.LastErrorText);
    return;
}

Debug.WriteLine("Number of parts: " + Convert.ToString(mime.NumParts));