How to iterate through component via .NET(such as C#, in DxD or XDx)

Hi Guys,

     I'm trying to iterate through component via .NET, but it does not work.

     By using "COM Interop" , I got file named "Interop.ViewDraw.dll" .

     But the code segment below could not work at all:

     ViewDraw.ApplicationDxAppHandle = (ViewDraw.Application)System.Runtime.InteropServices.Marshal.GetActiveObject("ViewDraw.Application");

     ViewDraw.IVdSchematicSheetDocumentstempSSD =  DxAppHandle.SchematicSheetDocuments();   // tempSSD has counter, butCANNOTiterate through

     ViewDraw.IVdObjsDesignObjects = DxAppHandle.Query(ViewDraw.VdObjectTypeMask.VDM_COMP, ViewDraw.VdAllOrSelected.VD_ALL);   // CANNOTagain

     This problem has troubled me a few weeks, how can I fix it?

      Any hints are welcome!