This gets the material id that is associated with the element in the current export state.
Namespace: Autodesk.Revit.DB.IFC
Assembly: RevitAPIIFC (in RevitAPIIFC.dll) Version: 25.0.0.0 (25.0.0.0)
public ElementId GetMaterialIdForCurrentExportState()
ElementId The material id.
Even though there could be several materials associated with the element (set during PushExportState()), unless the element has support for IfcMaterialLayerSet, IFC output will include only this one.