<div class="UserTree">
  <ul id="treeDemo" class="ztree"></ul>
</div>

<script>
  var zNodes;
  var zTree;
  $(function () {
    $.ajax({
      cache: true,
      type: "get",
      url: "/User/NextLeve",
      async: false,
      success: function (data) {
        zNodes = data;
      },
      error: function (data) {
        alert("error");
      }
    });
    zTree = ZTreeCustom.init($("#treeDemo"), setting, zNodes);
    zTree.expandAll(false);
  })
  var setting = {
    view: {
      nameIsHTML: true
    },
    data: {
      simpleData: {
        enable: true
      },
      keep: {
        parent: true
      }
    },
    open: false,
    callback: {
      onClick: nodeClick,
      onExpand: function (event, treeId, treeNode) {
        addSubNode(treeNode);
      }
    }
  };
  function showIconForTree(treeId, treeNode) {
    return !treeNode.isParent;
  };
  function searchM() {
    var username = $("#txtName").val()
  }
  function nodeClick(event, treeId, treeNode, clickFlag) {
    addSubNode(treeNode);
  }
  function addSubNode(treeNode) {
    if (!treeNode.isParent) return;
    var s = treeNode.children;
    if (s != undefined)
      return;
    $.ajax({
      cache: true,
      type: "get",
      url: "/User/NextLeve",
      data: { userId: treeNode.id },
      async: true,
      success: function (data) {
        zTree.addNodes(treeNode, data);
      },
      error: function (data) {
        alert("error");
      }
    });
  }
</script>

public class UserNode
{
  public long id { get; set; }
  public long pId { get; set; }
  public string name { get; set; }
  public bool open { get; set; }
  public bool isParent { get; set; }
  public string icon { get; set; }
}