(SQL Server) 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.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

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

    DECLARE @mime int
    EXEC @hr = sp_OACreate 'Chilkat.Mime', @mime OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    -- Create a multipart/mixed MIME message with two sub-parts.
    -- We'll use the Base64 encoding for the 2nd sub-part.
    DECLARE @part1 int
    EXEC @hr = sp_OACreate 'Chilkat.Mime', @part1 OUT

    EXEC sp_OAMethod @part1, 'SetBodyFromPlainText', @success OUT, 'This is part 1'

    DECLARE @part2 int
    EXEC @hr = sp_OACreate 'Chilkat.Mime', @part2 OUT

    EXEC sp_OAMethod @part2, 'SetBodyFromPlainText', @success OUT, 'This is part 2'
    EXEC sp_OASetProperty @part2, 'Encoding', 'base64'

    EXEC sp_OAMethod @mime, 'NewMultipartMixed', @success OUT
    EXEC sp_OASetProperty @mime, 'UseMmDescription', 0
    EXEC sp_OAMethod @mime, 'AppendPart', @success OUT, @part1
    EXEC sp_OAMethod @mime, 'AppendPart', @success OUT, @part2

    -- Show the MIME message:
    EXEC sp_OAMethod @mime, 'GetMime', @sTmp0 OUT
    PRINT @sTmp0

    -- 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)
    DECLARE @n int
    EXEC sp_OAGetProperty @mime, 'NumParts', @n OUT

    PRINT 'Num Parts = ' + @n

    EXEC sp_OAMethod @mime, 'GetBodyDecoded', @sTmp0 OUT
    PRINT 'Body = ' + @sTmp0

    -- The GetEntireBody retrieves the entire content after
    -- the header.  (Perhaps GetEntireBody should've been named
    -- GetEntireContent to make it less confusing...)

    PRINT '---- EntireBody:'
    EXEC sp_OAMethod @mime, 'GetEntireBody', @sTmp0 OUT
    PRINT @sTmp0

    PRINT '********'

    -- 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.
    DECLARE @part int
    EXEC @hr = sp_OACreate 'Chilkat.Mime', @part OUT

    EXEC sp_OAMethod @mime, 'PartAt', @success OUT, 1, @part


    PRINT 'Decoded Body:'
    EXEC sp_OAMethod @part, 'GetBodyDecoded', @sTmp0 OUT
    PRINT @sTmp0

    PRINT 'Encoded Body:'
    EXEC sp_OAMethod @part, 'GetBodyEncoded', @sTmp0 OUT
    PRINT @sTmp0

    EXEC @hr = sp_OADestroy @mime
    EXEC @hr = sp_OADestroy @part1
    EXEC @hr = sp_OADestroy @part2
    EXEC @hr = sp_OADestroy @part


END
GO