(Classic ASP) MIME Body vs. Sub-Parts

Explains the difference between sub-parts and body.

MIME documents (i.e. messages) can have a nested structure. The simplest MIME message contains a header followed by content (possibly encoded). The header is delimited from the content by two consecutive CRLF's.

A MIME message may be multipart. If so, then the Content-Type header field indicates "multipart" and the content the follows the header is itself a MIME message, which may also be multipart, etc. You can see how MIME messages effectively have a tree structure. The non-leaf nodes have Content-Types that are "multipart/" and the leaf nodes have non-multipart Content-Types.

The Chilkat MIME component/library uses two terms that need to be understood in order to effectively use the API. These are "body" and "sub-part". A multipart node has 1 or more sub-parts, but its body is empty. A leaf node (i.e. non-multipart node) has no sub-parts, but the body is (usually) non-empty.

This example creates a multipart MIME message and shows the results of getting the sub-parts and body of each node.

Note: This example requires Chilkat v11.0.0 or greater.

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<%
success = 0

' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

set mime = Server.CreateObject("Chilkat.Mime")

' Create a multipart/mixed MIME message with two sub-parts.
' We'll use the Base64 encoding for the 2nd sub-part.
set part1 = Server.CreateObject("Chilkat.Mime")
success = part1.SetBodyFromPlainText("This is part 1")

set part2 = Server.CreateObject("Chilkat.Mime")
success = part2.SetBodyFromPlainText("This is part 2")
part2.Encoding = "base64"

success = mime.NewMultipartMixed()
mime.UseMmDescription = 0
success = mime.AppendPart(part1)
success = mime.AppendPart(part2)

' Show the MIME message:
Response.Write "<pre>" & Server.HTMLEncode( mime.GetMime()) & "</pre>"

' Here's the MIME:
' Content-Type: multipart/mixed;
' 	boundary="------------040605030407000302060008"
' 
' --------------040605030407000302060008
' Content-Type: text/plain;
' 	 charset="us-ascii"
' Content-Transfer-Encoding: 7bit
' 
' This is part 1
' --------------040605030407000302060008
' Content-Type: text/plain;
' 	 charset="us-ascii"
' Content-Transfer-Encoding: base64
' 
' VGhpcyBpcyBwYXJ0IDI=
' 
' --------------040605030407000302060008--

' If we examine the root node of the MIME message, 
' we see that it has 2 sub-parts and the body is empty (as expected)
n = mime.NumParts
Response.Write "<pre>" & Server.HTMLEncode( "Num Parts = " & n) & "</pre>"
Response.Write "<pre>" & Server.HTMLEncode( "Body = " & mime.GetBodyDecoded()) & "</pre>"

' The GetEntireBody retrieves the entire content after
' the header.  (Perhaps GetEntireBody should've been named
' GetEntireContent to make it less confusing...)
Response.Write "<pre>" & Server.HTMLEncode( "---- EntireBody:") & "</pre>"
Response.Write "<pre>" & Server.HTMLEncode( mime.GetEntireBody()) & "</pre>"
Response.Write "<pre>" & Server.HTMLEncode( "********") & "</pre>"

' Now examine the 2nd sub-part.  It has a body encoded
' using base64.  Get the contents of the body in both
' decoded and encoded forms:

' index 0 is the 1st part, index 1 is the 2nd part.
set part = Server.CreateObject("Chilkat.Mime")
success = mime.PartAt(1,part)

Response.Write "<pre>" & Server.HTMLEncode( "Decoded Body:") & "</pre>"
Response.Write "<pre>" & Server.HTMLEncode( part.GetBodyDecoded()) & "</pre>"
Response.Write "<pre>" & Server.HTMLEncode( "Encoded Body:") & "</pre>"
Response.Write "<pre>" & Server.HTMLEncode( part.GetBodyEncoded()) & "</pre>"

%>
</body>
</html>