System.Xml.Xsl.XmlQueryTypeFactory.ParentOf C# (CSharp) Method

        public XmlQueryType ParentOf(XmlQueryType source, XmlQueryType filter) {
            Debug.Assert(filter.IsNode && filter.Count == 1 && filter.IsSingleton);
            List<XmlQueryType> list = new List<XmlQueryType>();
            XmlQueryCardinality card = XmlQueryCardinality.None;

            foreach (XmlQueryType sourceItem  in source) {
                switch (sourceItem.TypeCode) {
                case XmlTypeCode.Node:
                case XmlTypeCode.ProcessingInstruction:
                case XmlTypeCode.Comment:
                case XmlTypeCode.Text:
                case XmlTypeCode.Element:
                    if (schemaSet == null) {
                        card |= AddFilteredPrime(list, UntypedDocument, filter) * XmlQueryCardinality.ZeroOrOne;
                        card |= AddFilteredPrime(list, UntypedElement, filter) * XmlQueryCardinality.ZeroOrOne;
                    }
                    else {
                        card |= AddFilteredPrime(list, Document, filter) * XmlQueryCardinality.ZeroOrOne;
                        card |= AddFilteredPrime(list, Element, filter) * XmlQueryCardinality.ZeroOrOne;
                    }
                    break;

                case XmlTypeCode.Namespace:
                case XmlTypeCode.Attribute:
                    if (schemaSet == null) {
                        card |= (AddFilteredPrime(list, UntypedElement, filter) * XmlQueryCardinality.ZeroOrOne);
                    }
                    else {
                        card |= (AddFilteredPrime(list, Element, filter) * XmlQueryCardinality.ZeroOrOne);
                    }
                    break;

                case XmlTypeCode.Document:
                    card |= XmlQueryCardinality.Zero;
                    break;

                default:
                    Debug.Assert(sourceItem.IsAtomicValue, "missed case for a node");
                    break;
                }
            }
            // Make sure that cardinality is at least Zero
            return PrimeProduct(ChoiceType.Create(list), source.Cardinality * card);
        }