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I'm having to update one of our ancient Intranet applications that was written in Classic ASP and utilizes an in-house COM+ Service. I cannot find the source code to this object anywhere and it was not documented by the developer.

I can view the methods available in the Service through Start -> Administrative Tools -> Component Services but can't for the life of me figure out how to look inside the methods to see what they're doing.

Is there anyway to decompile these COM+ Services, or otherwise see what their methods do, or am I doomed to pure observation of the old application and try my best to mimic the behavior and data?

Note: I exported the service from the old server, installed in on my dev box, added the reference to a VS2010 project, and tried to discern these methods using the Object Explorer. Nothing...

dthorpe
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Chiramisu
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COM services include type descriptions of what methods exist on the COM classes and their parameters so that automation controllers can figure out how to pass parameters to the COM methods.

Beyond that, though, there is nothing to indicate what the COM classes do internally other than the native x86 machine code itself. You can try using an x86 disassembler on the DLL, but unless you are already familiar with x86 machine code instructions, this won't be a lot of help.

Compiling source code down to native machine code throws away an enormous amount of information. Variable names, internal function names, none of that is needed for the CPU to execute instructions and perform the operations indicated by the original source code. It is virtually impossible for disassemblers to reconstitute these names that would be helpful clues as to what the code is intended to do. A disassembler can sometimes help figure out core logic, but it will require a lot of careful analysis and effort by a person to even scratch the surface. It's like trying to understand the forest by looking at individual blades of grass.

dthorpe
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  • Thank you sir for your answer. It seems these methods primarily just fetch data from a database. I've determined the connection string from the global.asa file. Is there a way I could at least determine the SQL selection command by decompiling? If so, where can I get the DLL? All I was able to export was a *.CAB file containing an MSI installer. – Chiramisu Feb 20 '13 at 01:32
  • You will need to install the COM component in order to poke around in its DLLs. Disassembling the DLL may be able to show you string fragments used by the DLL to form a SQL query. If you're lucky, the SQL query you're looking for is in one parameterized string constant. If you're not so lucky, the DLL constructs the SQL query using lots of little string concat operations, in which case there will be very little to see in disassembled code. Installing the DLL should also enable you to call the DLL methods and step through the asm code in a debugger. – dthorpe Feb 20 '13 at 18:44