System.Xml.Xsl.XsltOld.XsltCompileContext.BuildKeyTable C# (CSharp) Method

        private Hashtable BuildKeyTable(Key key, XPathNavigator root) {
            Hashtable keyTable = new Hashtable();

            string matchStr = this.processor.GetQueryExpression(key.MatchKey);
            Query matchExpr = this.processor.GetCompiledQuery(key.MatchKey);
            Query useExpr   = this.processor.GetCompiledQuery(key.UseKey);

            XPathNodeIterator  sel = root.SelectDescendants(XPathNodeType.All, /*matchSelf:*/ false);

            while(sel.MoveNext()) {
                XPathNavigator node = sel.Current;
                EvaluateKey(node, matchExpr, matchStr, useExpr, keyTable);
                if (node.MoveToFirstAttribute()) {
                    do {
                        EvaluateKey(node, matchExpr, matchStr, useExpr, keyTable);
                    } while (node.MoveToNextAttribute());
                    node.MoveToParent();
                }
            }
            return keyTable;
        }

            public override object Invoke(XsltContext xsltContext, object[] args, XPathNavigator docContext)
            {
                XsltCompileContext xsltCompileContext = (XsltCompileContext)xsltContext;

                string local, prefix;

                PrefixQName.ParseQualifiedName(ToString(args[0]), out prefix, out local);
                string?          ns      = xsltContext.LookupNamespace(prefix);
                XmlQualifiedName keyName = new XmlQualifiedName(local, ns);

                XPathNavigator root = docContext.Clone();

                root.MoveToRoot();

                ArrayList?resultCollection = null;

                foreach (Key key in xsltCompileContext._processor !.KeyList !)
                {
                    if (key.Name == keyName)
                    {
                        Hashtable?keyTable = key.GetKeys(root);
                        if (keyTable == null)
                        {
                            keyTable = xsltCompileContext.BuildKeyTable(key, root);
                            key.AddKey(root, keyTable);
                        }

                        XPathNodeIterator?it = args[1] as XPathNodeIterator;
                        if (it != null)
                        {
                            it = it.Clone();
                            while (it.MoveNext())
                            {
                                resultCollection = AddToList(resultCollection, (ArrayList?)keyTable[it.Current !.Value]);