public static JsTree showInTreeView(this JsTree jsTree, Panel topPanel) { var treeView = topPanel.add_TreeView(); Action<TreeNode,List<JsTreeNode>> addJsTreeNodes = (treeNode, jsTreeNodes)=>{ foreach(var jsTreeNode in jsTreeNodes) treeNode.add_Node(jsTreeNode.str() , jsTreeNode , jsTreeNode.children.size()>0); }; treeView.beforeExpand<JsTreeNode>( (treeNode,jsTreeNode)=>{ addJsTreeNodes(treeNode, jsTreeNode.children); }); addJsTreeNodes(treeView.rootNode(), jsTree.data); return jsTree; }