How to exclude custom OdDbEntity from selection?

You can use selection filter in OdDbSelectionSet query to exclude unnecessary entities from result selection set:

Code:

/** \details
    Filter selection only.  

    \param vpId [in]  id of OdDbViewportTableRecord  record or OdDbViewport entity in which to select.
    \param nPoints [in]  Number of points into selection shape.
    \param wcsPts [in]  Selection shape as set of World Coordinate Space points.
    \param mode [in]  Selection mode.
    \param sm [in]  Subentities selection mode.
    \param pFilter [in] object of type OdDbSelectionFilter or pointer to a OdResBuf chain defining the filter.
  */
  static OdDbSelectionSetPtr select(
    const OdDbObjectId& vpId,
    int nPoints,
    const OdGePoint3d* wcsPts,
    OdDbVisualSelection::Mode mode = OdDbVisualSelection::kCrossing,
    OdUInt32 sm = OdDbVisualSelection::kDisableSubents,
    const OdRxObject* pFilter = 0);