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

        private static void AddKeyValue(Hashtable keyTable, String key, XPathNavigator value, bool checkDuplicates) {
            ArrayList list = (ArrayList)keyTable[key];
            if (list == null) {
                list = new ArrayList();
                keyTable.Add(key, list);
            } else {
                Debug.Assert(
                    value.ComparePosition((XPathNavigator) list[list.Count - 1]) != XmlNodeOrder.Before,
                    "The way we traversing nodes should garantees node-order"
                );
                if (checkDuplicates) {
                    // it's posible that this value already was assosiated with current node
                    // but if this happened the node is last in the list of values.
                    if (value.ComparePosition((XPathNavigator) list[list.Count - 1]) == XmlNodeOrder.Same) {
                        return;
                    }
                } else {
                    Debug.Assert(
                        value.ComparePosition((XPathNavigator) list[list.Count - 1]) != XmlNodeOrder.Same,
                        "checkDuplicates == false : We can't have duplicates"
                    );
                }
            }
            list.Add(value.Clone());
        }