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Here's the scenario. I'm trying to access data in an Access 2007 db file. I can get this to work fine in Visual Studio using OLEDB with this provider... Provider=Microsoft.ACE.OLEDB.12.0
This works fine when compiled as a 32-bit dll. However, if I create a wrapper DLL and reference the 32-bit dll in LinqPad, then LinqPad throws the following.

An attempt was made to load a program with an incorrect format.

Well, a little research shows that message happens when you attempt to load a 32-bit dll into a 64-bit app.

It seems then, that Linqpad is runtime compiling itself as a 64-bit program since it's in a 64-bit environment, is this correct? Is it possible to force it compile as a 32-bit program so I can reverence native 32-bit dlls, perhaps with a command line switch?

To confirm this, I built the wrapper dll as a 64-bit program, and it throws the same error in a Visual Studio unit test. If I use the 64-bit wrapper dll in LinqPad then I get this...

InvalidOperationException: The 'Microsoft.ACE.OLEDB.12.0' provider is not registered on the local machine.

Research shows that this message indicates that the Access 32-bit dll is being loaded by a 64-bit app.

You can hack LINQPad so as to force 32-bit execution with the corflags tool:

corflags /32bit+ /force linqpad.exe

Bear in mind that you'll have to repeat the process after a LINQPad update. (It's also possible that it may prevent LINQPad updates from loading, because the signature will be missing from the original).

Regards

Joe