Question

我正在使用JSTree和一个MVC项目，我正在尝试将子节点添加到树中，但是我得到一个空引用错误对象引用未设置为行subGroupNode.children.Add(itemNode);上的对象实例我猜测这是因为subGroupNode.Children是空的。如何在前一个foreach循环中创建子项时。

    public JsonResult GetJsTree3Data()
    {
        var marketGroups = new List<JsTree3Node>();

        // Create our root node and ensure it is opened
        var root = new JsTree3Node()
        {
            id = Guid.NewGuid().ToString(),
            text = "Market Items",
            state = new State(true, false, false)
        };

        foreach (var group in GenerateGroups(connString))
        {
            if (group.marketParentGroup == 0)
            {
                var node = JsTree3Node.NewNode(group.id_str);
                node.text = group.name;
                node.state = new State(false, false, false);
                marketGroups.Add(node);
            }
        }

         foreach (var marketGroup in marketGroups)
        {
            foreach (var subGroup in GenerateGroups(connString))
            {
                if (subGroup.marketParentGroup.ToString() == marketGroup.id)
                {
                    var childNodes = new List<JsTree3Node>();

                    var childNode = new JsTree3Node();
                    childNode.id = subGroup.id_str;
                    childNode.text = subGroup.name;
                    childNode.state = new State(false, false, false);

                    childNodes.Add(childNode);

                    var subGroupNode = new JsTree3Node();
                    subGroupNode.id = subGroup.id_str;
                    subGroupNode.text = subGroup.name;
                    subGroupNode.state = new State(false, false, false);
                    subGroupNode.children = childNodes;

                    marketGroup.children.Add(subGroupNode);
                }
            }
        }

        return Json(root, JsonRequestBehavior.AllowGet);
    }

Answer 1

我通过创建与第一个列表相同的第二个列表并比较这两个列表来解决问题。

 public JsonResult GetJsTree3Data()
    {
        var marketGroups = new List<JsTree3Node>();
        var marketSubGroups = new List<JsTree3Node>();

        foreach (var group in GenerateGroups(connString))
        {
            var node = JsTree3Node.NewNode(group.id_str);
            node.text = group.name;
            node.state = new State(false, false, false);
            node.parentId = group.marketParentGroup;
            marketSubGroups.Add(node);
        }

        // Create our root node and ensure it is opened
        var root = new JsTree3Node()
        {
            id = Guid.NewGuid().ToString(),
            text = "Market Items",
            state = new State(true, false, false)
        };

        foreach (var group in marketSubGroups)
        {
                var node = JsTree3Node.NewNode(group.id);
                node.text = group.text;
                node.state = new State(false, false, false);
                marketGroups.Add(node);
        }

        foreach (var marketGroup in marketGroups)
        {
            foreach (var subGroup in marketSubGroups)
            {
                if (subGroup.parentId.ToString() == marketGroup.id)
                {
                    var subGroupNode = new JsTree3Node();
                    subGroupNode.id = subGroup.id;
                    subGroupNode.text = subGroup.text;
                    subGroupNode.state = new State(false, false, false);
                    marketGroup.children.Add(subGroupNode);
                }
            }
        }

        root.children = marketGroups;

        return Json(root, JsonRequestBehavior.AllowGet);
    }

JSTree向子节点添加节点

1 个答案: