The BadImageFormatException when loading a dll is caused by incompatible bitness (32 or 64-bit) on the solution/project vs. the DLL.
To resolve the error, you can either:
– Change target platform to x86 in your Visual Studio solution
– If you want to build a 64-bit application, change the references for the two DLLs Tobii.EyeX.Client.dll and Tobii.EyeX.Client.Net20.dll to the 64-bit versions, located in \lib\x64
Hopefully once you get the Activatable Buttons sample going, it should clear up your remaining doubts.
Please let us know how you get on.