I need to integrate some legacy 32-bit code – for which I don’t have the source code, into a project in such a way that it can be called from a 64-bit .NET assembly. The original code is implemented as a 32-bit COM object in a DLL. Windows doesn’t allow direct calls from 64 to 32-bit objects, so I’m looking for inspiration on how to deal with this situation.
How can a legacy 32-bit COM object be accessed from a 64-bit .NET assembly?
UPDATE: We discovered that the COM component was itself a wrapper around some ANSI C, which we founf the original source for. We were able to compile that in Visual Studio as a native 64-bit dll, and import that into .NET – sorry to move the goalposts!
The best approach is to make an out of process COM server that wraps your 32-bit DLL. You can then call this from 64bit code.
Here is an explanation of the basic concepts.