64 to 32 bit Interop - how?

Question

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 or

Answer 1

Check out this blog post. You can reference a 32 bit COM assembly from a 64 bit .NET application using a runtime callable wrapper. The short version is the following...

1. Use tlbimp.exe to create a 64 bit Runtime Callable Wrapper:

   tlbimp.exe foo.dll /machine:x64 /out:Interop.Foo.dll

2. Register the COM assembly (not the RCW) if you haven't already:

   regsvr32.exe foo.dll

3. Reference the RCW (eg. Interop.Foo.dll) from your application. Change your Build Configuration to x64 and let 'er rock.