Loading failed with "marshaling conversion 22 not implemented"

[blackdeng]

I'm integrating the Image3dAPI and the GE loader to a Unity project. Based on the TestViewer example, it looks like the Image3dAPI can be integrated as a managed plugin to Unity. I was able to retrieve information such as the bounding box, and frame count in my Unity C# code, but when I try to access the data using GetFrame, an exception was thrown "marshaling conversion 22 not implemented". Further stack trace attached below:

  at (wrapper managed-to-native) Image3dAPI.IImage3dSource.GetFrame(intptr,uint,Image3dAPI.Cart3dGeom,uint16[],Image3dAPI.Image3d&)
  at (wrapper cominterop) Image3dAPI.IImage3dSource.GetFrame(uint,Image3dAPI.Cart3dGeom,uint16[])
  at (wrapper cominterop-invoke) Image3dAPI.IImage3dSource.GetFrame(uint,Image3dAPI.Cart3dGeom,uint16[])

It seems the exception is because Unity C# uses Mono scripting backend which does not support SAFEARRAY in runtime. All APIs that return SAFEARRAY failed in Unity (returns null instead). Would it be possible to use a alternative type for arrays so that the library can be used in Unity?