ReferenceDim.cs

public static Reference Reference(Element Familyinstance)
        {
            FamilyInstance familyInstance = (FamilyInstance)Familyinstance.InternalElement;
            Options options = new Options();
            options.ComputeReferences = true;
            options.IncludeNonVisibleObjects = true;
            var result = familyInstance.get_Geometry(options)
                .OfType<Autodesk.Revit.DB.Point>()
                .FirstOrDefault();
            if (result == null) return null;

            return result.Reference;
        }