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    <p>Technically, you're not implementing the interfaces in C++ but MIDL. It's a separate interface language and it's worth knowing if you're going to do COM work.</p> <p>Anyway, it's not uncommon to use .NET interops to implement COM objects, but the two are not really compatible technologies. You WILL run into gotchas unless you're writing very simple objects.</p> <p>To get you started, here's some random assortment of pointers along with a couple of articles that I've used in the past.</p> <ul> <li>COM is an interface-driven technology. Repeat that to yourself again and again.</li> <li>Develop the interface definition separately, using MIDL.</li> <li>COM garbage collection is deterministic (reference counting), but this starts to fall apart when used with .NET, where the garbage collection happens automatically and unpredictably.</li> <li>Dealing with Eventsinks/event handlers is ugly.</li> </ul> <p>A small taste of the type of headaches you'll run into: <a href="http://www.codeproject.com/KB/cs/LingeringCOMObjects.aspx" rel="nofollow noreferrer">http://www.codeproject.com/KB/cs/LingeringCOMObjects.aspx</a></p> <p>More on why you should NOT let Visual Studio auto-generate the COM interface for you: <a href="http://blogs.msdn.com/mbend/archive/2007/04/17/classinterfacetype-none-is-my-recommended-option-over-autodispatch-autodual.aspx" rel="nofollow noreferrer">http://blogs.msdn.com/mbend/archive/2007/04/17/classinterfacetype-none-is-my-recommended-option-over-autodispatch-autodual.aspx</a></p> <p>Bridging events: <a href="http://www.west-wind.com/presentations/dotnetfromVfp/DotNetFromVfp_EventHandling.asp" rel="nofollow noreferrer">http://www.west-wind.com/presentations/dotnetfromVfp/DotNetFromVfp_EventHandling.asp</a></p>
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    1. POCreating COM extension using C# - is it worth it?
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    1. UShythlodayr
    1. UShythlodayr
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    1. CO+1 Especially for the Eventsinks bullet. This has been a huge issue for me in the past.
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      1. USMatt Spradley
    2. COThanks for the links! The MIDL definition already exists - that's exactly the issue: how do I translate the MIDL interface definition into .NET, as my understanding is that exposing .NET libaries to COM does not involve MIDL (am I wrong?) Events are luckily not an issue. All the COM does are explicit function calls of the set/get type. So it is probably a fairly simple object.
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      1. USAndreas F
    3. COExposing .NET libraries to COM doesn't HAVE to involve MIDL, but it's bad practice to let Visual Studio auto-generate the interface definitions for you. In your situation, you're lucky so I think it builds a stronger case for trying out the interop solution. Anyway, the second link I gave you gives you a very small example of how implement an interface using C# so I think you're good to go.
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