Returns the ID of the material object associated with the layer record object (DXF 347) or OdDb::kNULL when the layer is not associated with material. This material is used when the Material property of an entity belonged to this layer is set to ByLayer value.

Example of Working with the Layer Record Object 

Specific Properties of Layers 

OdDbLayerTableRecord::setMaterialId() method

OdDbLayerTableRecord Methods