The Id of the element assocated with this material in the model.
Namespace: Autodesk.Revit.DB
Assembly: RevitAPI (in RevitAPI.dll) Version: 25.0.0.0 (25.0.0.0)
public ElementId MaterialId { get; }
It is possible that no specific material is applied to a face, in which case the default material is used, and this property returns an InvalidElementId.