Add new menu using SiteMapNode but not applying selected menu style

I have implemented a new plugin which is having a few menus. It showing in the sidebar menu correctly. But the problem is when the user goes to the page, It is not applying class ="active current-active-item" into the menu list item.

var pluginNode = rootNode.ChildNodes.FirstOrDefault(x => x.SystemName == "Purchasing");
                if (pluginNode == null)
                {
                    var menuItem = new SiteMapNode()
                    {
                        Title = "Purchasing",
                        Visible = true,
                        SystemName = "LabFriend.PurchaseOrderSync",
                        IconClass = "fa fa-puzzle-piece",
                        RouteValues = new RouteValueDictionary() { { "area", null }}
                    };
                    rootNode.ChildNodes.Add(menuItem);
                }


                var menuPurchaseOrder = new SiteMapNode()
                {
                    SystemName = "LabFriend.BackorderPurchaseOrdersSync",
                    Title = "Purchase Orders Report",
                    ControllerName = "BackorderPurchaseOrder",
                    ActionName = "Index",
                    Visible = true,
                    IconClass = "fa-dot-circle-o",
                    RouteValues = new RouteValueDictionary() { { "area", "admin" } }
                };
                rootNode.ChildNodes.Where(x => x.Title == "Purchasing").FirstOrDefault().ChildNodes.Add(menuPurchaseOrder);