Question

All,

I have a .NET managed application which runs in 32bit machines.
I am fine with compiling it to 64bit and port it on a 64bit machine.
However I depend on some 3rd party DLLs which are 32 bit assemblies.
Can I mix 64bit and 32bit assemblies together executing on a 64bit machine?

Thanks !

Answer 1

Not if they are running in the same process.

A process on the OS cannot load assemblies of different “bit-ness”. Once chosen, all assemblies have to conform. You will get a BadImageFormatException usually if you attempt to load a 32-bit DLL into a 64-bit process or vice versa.

Three options:

1. Get 64-bit versions of the problem DLLs (ideal).
2. Run exclusively in 32-bit all the time (usually the chosen path).
3. Run the problem DLLs in another process and use something like IPC to talk across the process boundary (extreme, but I’ve had to do this once).

There is nothing inherently wrong with running in 32-bit on a 64-bit OS, don’t fall into the trap of thinking it will be slower.