参考文档：
https://www.cnblogs.com/luozhihao/p/4679050.html
http://jsfiddle.net/vakata/2kwkh2uL/5/
核心的关键点是：
组装节点的children元素时，设置 children = true
$('#jstree_company').jstree({
"core": {
"animation": 0,
"check_callback": true,
"themes": { "stripes": true },
'data': {
'url': function (node) {
return '/IS/CDictionary/GetDictionTree';
},
'data': function (node) {
return { 'id': node.id,'type':'company' };
}
}
},
"plugins": ["contextmenu", "dnd"],
});
组装的后台代码：
JSTree treeFlow = new JSTree()
{
id = item.DictID.ToString(),
parent = id,
text = item.Title,
state = new NodeState() { opened = false },
children = true
};
trees.Add(treeFlow);