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    Geek-O-Terica 16: Easy conversion of Notes documents to MIME format (Part 2)

    Bob Balaban  April 4 2011 05:45:00 AM
    Greetings, Geeks!

    Recently I posted some sample code showing you how to convert Notes documents to MIME format on disk, using the Notes Java APIs. Unfortunately, if you need to do this kind of conversion using some other platform (such as .net), the job is a bit harder. A key method on the Document class (doc.convertToMIME()) is missing in the COM classes for Notes. Why? No idea, someone should ask Lotus about that. Probably has something to do with fear (but that's just speculation on my part).

    No worries, though. the convertToMIME() method uses public C API calls to do its work, so we can do the same from a .net program. For starters, see my blog post on calling C API from C# (c-sharp) programs, here. That post talks about the basic techniques and syntax for setting up any kind of call-out from C# to C, so I won't repeat that here (the idea is just about the same if you're using vb). Here's a c-sharp file that provides a bunch of wrappers for Notes C API calls, bundled together in a class called NotesEntriess.NotesEntries.cs  

    The tedious bit about doing MIME conversion for a .net program is that there are several C calls you have to make for the 1 Java/LotusScript call. The tricky part is that, to do it without having to do everything at the C API level, you want to save typing by leveraging the COM classes, and only use the NotesEntries wrappers when you have to. The problem is that the COM classes do not expose the in-memory "handle" for a NotesDocument instance -- you can only get the Note ID -- while the C API calls require the handle for most things.

    So you'll see in the sample program "BlogMIME.cs" (BlogMIME.cs) that the first part of the work (converting a document to MIME format in memory) is done with C API wrappers (after using "regular" COM classes to access the NSF and find the document in the first place, of course). I could have continued to use the C API to iterate over MIMEParts in the converted document, force Base64 encoding, and write out the results, but it's really much easier to do all that using COM classes. Unfortunately, there's no way to take the NOTEHANDLE that I get using the C API and use it to get a NotesDocument COM object. I had to save() the document back to disk, get the Note ID, and use that to "get" the document again via COM. There's a slight performance hit for the extra save, but it was worth it in this case.

    You'll notice that the c# code that actually writes out the converted MIME document to disk is almost a line-for-line translation of the Java code I posted earlier. That's possible because the Notes COM classes are almost identical (on purpose) to the Java and LotusScript interfaces. The only reason we have to get tricky with using C API wrappers is that the Document.convertToMIME() function is missing in the COM interface.

    There are some other nice (reusable) features of the c# code, such as mapping various C constants to c# syntax, and so on. So, take the code, use it as a source of techniques for doing this kind of integration.  Enjoy!

    Geek ya later.

    (Need expert application development architecture/coding help?  Want me to help you invent directory services based on RDBMS? Need some Cloud-fu or some web services? Contact me at: bbalaban, gmail.com)
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