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Help referencing a 32-bit DLL in a 64-bit application


This is my first post on this forum. If I have not followed any standard etiquette or need to provide more information, please advise.

I have a Microsoft Project Add-In written in VB.NET (Visual Studio 2015) that I would like to make compatible with both the 32-bit and 64-bit environments of MS Project (2010+). The add-in would work in both, except we are referencing a custom, legacy DLL written in VB6 that is not compatible with the 64-bit Project environment.

We attempt to access this VB6 DLL's functionality by creating an object of it in the VB.NET code using the CreateObject() function. This results in 'Runtime Error (429): ActiveX can't create component' error in the 64-bit environment. It works fine for 32-bit.

Is there any way to create my object reference to this VB6 DLL without upgrading the legacy code to VB.NET?

Thank you for your time.
Christopher Baugh
Christopher Baugh
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Fernando SotoRetiredCommented:
To your statement, " I would like to make compatible with both the 32-bit and 64-bit environments of MS Project (2010+).", the best way to get this to work is to compile the .Net application for a 32 bit platform / x86. In this way it will run on both 32 bit and 64 bit, on a 64 bit system in will run in WOW64 which is part of the operating system. The next best option would be to rewrite the 32 bit dll to 64 bit. The last option would be a com object for the 32 bit dll and and modify the code in the .Net application to access the dll through IPC, Inter Process Communication, to access the dll functions. if you take this route please read this article Accessing 32-bit DLLs from 64-bit code.
Fernando SotoRetiredCommented:
I gave three possible solutions to the question.
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