Why this topic becomes sticky
32-bit / 64-bit issues are usually not just build-setting problems. They tend to involve process boundaries, native DLL calls, existing COM assets, and whether C++/CLI should exist in the design at all.
That is why fixing only the visible error often does not solve the real project-level problem.
Questions that usually need to be clarified
- how to handle assets that must remain on the 32-bit side
- how to cut the boundary between newer .NET code and native DLLs
- whether C++/CLI is the right bridge or whether P/Invoke is enough
- how deployment and runtime constraints affect the design
Typical direction
For interoperability-heavy work, it is usually better to decide the boundary design before rushing into feature changes. The related articles and service pages linked from here are meant to help make that decision practical rather than abstract.