System.Xml.Xsl.Qil.QilPatternFactory.And C# (CSharp) Method

        public QilNode And(QilNode left, QilNode right) {
            CheckLogicArg(left);
            CheckLogicArg(right);

            if (! debug) {
                // True, True => True (right)          other, True => other (left)
                // True, False => False (right)        other, False => False (right)
                // True, other => other (right)        other, other => And
                if (left.NodeType == QilNodeType.True || right.NodeType == QilNodeType.False) {
                    return right;
                }
                if (left.NodeType == QilNodeType.False || right.NodeType == QilNodeType.True) {
                    return left;
                }
            }
            return f.And(left, right);
        }

        private static QilLoop BuildAxisFilter(QilPatternFactory f, QilIterator itr, XPathAxis xpathAxis, XPathNodeType nodeType, string name, string nsUri) {
            QilNode nameTest = (
                name  != null && nsUri != null ? f.Eq(f.NameOf(itr), f.QName(name, nsUri))    : // ns:bar || bar
                nsUri != null                  ? f.Eq(f.NamespaceUriOf(itr), f.String(nsUri)) : // ns:*
                name  != null                  ? f.Eq(f.LocalNameOf(itr), f.String(name))     : // *:foo
                /*name  == nsUri == null*/       f.True()                                       // *
            );

            XmlNodeKindFlags intersection = XPathBuilder.AxisTypeMask(itr.XmlType.NodeKinds, nodeType, xpathAxis);

            QilNode typeTest = (
                intersection == 0                     ? f.False() :  // input & required doesn't intersect
                intersection == itr.XmlType.NodeKinds ? f.True()  :  // input is subset of required
                /*else*/                                f.IsType(itr, T.NodeChoice(intersection))
            );

            QilLoop filter = f.BaseFactory.Filter(itr, f.And(typeTest, nameTest));
            filter.XmlType = T.PrimeProduct(T.NodeChoice(intersection), filter.XmlType.Cardinality);

            return filter;
        }