// View management (menu handlers)

        protected void ShowPropertyGrid(object sender, EventArgs args)
        {
            PropertyGridController.IfNull(() =>
            {
                NewDocument("propertyGrid.xml");
            });
        }
        protected void LoadSymbols()
        {
            XmlSerializer xs = new XmlSerializer(typeof(Schema));
            StreamReader  sr = new StreamReader(SchemaFilename);

            Schema = (Schema)xs.Deserialize(sr);
            sr.Close();
            SymbolEditorController.IfNotNull(ctrl => ctrl.PopulateTree());
            PropertyGridController.IfNotNull(pgrid => pgrid.View.ShowObject(Schema));
            MruMenu.AddFile(SchemaFilename);
        }
        protected void CreateSymbolsRootNode()
        {
            SymbolEditorController.IfNotNull(ctrl => ctrl.View.Clear());
            schemaController = new GenericController <Schema>();
            Schema           = (Schema)schemaController.Instance;

            SymbolEditorController.IfNotNull(ctrl =>
            {
                ctrl.View.AddNode(schemaController, null);
                PropertyGridController.IfNotNull(pgrid => pgrid.View.ShowObject(Schema));
            });
        }