FMOD C# initialization error with imported function FMOD5_System_Create()

I am getting a returned exception while trying to use the function FMOD5_System_Create().

The exception is a System.BadImageFormatException.

Here is the code I am using to initialize fmod:

public struct Factory
{
public static RESULT System_Create(out System system)
{
return FMOD5_System_Create(out system.handle);
}

    #region importfunctions
    [DllImport(VERSION.dll)]
    private static extern RESULT FMOD5_System_Create(out IntPtr system);

    #endregion
}

If anyone can help me understand what is happening, I would be much appreciated.

It may be that the lib you are trying to use is for the wrong architecture or platform.