Object Filter

AcDbBasicFilter 

Filters objects (entities) in the current drawing based on layer, feature-class, and block criteria.
Filters are constructed with "*" as the default filtering value, indicating that all entities are to be filtered. Other valid values are "" (an empty string) to ignore entities during filtering, and NULL (a null filter) to exclude any entities returned by the filter set. The default AcDbBasicFilter object is constructed with “*” as the value for the Layers, FeatureClasses, and Blocks filtering criteria, and so will filter out classified blocks from all layers. The following table shows how to set entity-filtering criteria for various filtering scenarios. (Note that these scenarios do not include objects on frozen, locked, or off layers unless you have set the layer status mask with SetLayerStatusMask()).  

AcDbObjectFilter 

Base class for creating filters that filter objects (entities) in the current drawing based on the specified criteria. 

AcDbObjectFilterGroup 

Filters objects (entities) in the current drawing based on the criteria of one or more listed filters.