public class Unit
 {
 public decimal id { get; set; }
 public string text { get; set; }
 public string state { get; set; }
 public List<Unit> children { get; set; }
 public Unit ()
 {
 this.children = new List<Unit>();
 this.state = "open";
 }
 }

public class UnitComponent
 {
 ExeceteOralceSqlHelper SqlHelper= new ExeceteOralceSqlHelper();//数据库处理类
 public UnitParent GetUnit()
 {
  Unit rootUnit = new Unit();
  rootUnit.id = 1000;
  rootUnit.text = "BO API";
  rootUnit.children = GetUnitList(0);
  UnitRecursive(rootUnit.children);
  return rootUnit;
 }

 /// <summary>
 /// 递归查询部门
 /// </summary>
 /// <param name="units"></param>
 private void UnitRecursive(List<Unit> units)
 {
  foreach (var item in units)
  {
  item.children = GetUnitList(item.id);
  if (item.children != null && item.children.Count > 0)
  {
   item.state = "closed";
   UnitRecursive(item.children);
  }
  }
 }

 /// <summary>
 /// 通过parentID获取所有子部门
 /// </summary>
 /// <param name="parentID">父id</param>
 /// <returns>返回Unit集合</returns>
 private List<Unit> GetUnitList(decimal parentID)
 {
  List<Unit> unitLst = new List<Unit>();
  string sql = string.Format("select hh.unit_id,hh.unit_name from unit_main hh where hh.parent_id={0}", parentID);
  DataTable dt = SqlHelper.ExecuteDataTable(sql);//返回DataTable方法
  if (dt != null && dt.Rows.Count > 0)
  {
  for (int i = 0; i < dt.Rows.Count; i++)
  {
   Unit dtup = new Unit()
   {
   id = Convert.ToInt32(dt.Rows[i]["unit_id"]),
   text = dt.Rows[i]["unit_name"].ToString()
   };
   unitLst.Add(dtup);
  }
  }
  return unitLst;
 }
}

public void ProcessRequest(HttpContext context)
{
 JavaScriptSerializer js = new JavaScriptSerializer();
 context.Response.ContentType = "application/json";
 UnitComponent uc = new SynUser.UnitComponent();
 var unit = uc.GetUnit();
 context.Response.Write("[" + js.Serialize(unit) + "]");
}

<asp:TextBox ID="tbUnit" runat="server" Width="280px"></asp:TextBox>

$('#tbUnit').combotree({
 url: , '/unit.ashx'
 cascadeCheck: true,
 placeholder: "请选择部门",
 method: 'get',
 required: true,
 multiple: true,
 onChange: function (newValue, oldValue) {
 computeunit();
 },
 onLoadSuccess: function (node, data) {
    
 }
});

function computeunit() {
  var arr = new Array();
  var selectstr = $("#tbUnit").combotree("getValues").toString();
  var select = selectstr.split(",");
  var t = $('#tbUnit').combotree('tree'); // get the tree object
  var n = t.tree('getChecked'); // get selected node
  unitrecursive(t, n, arr);
  alert(subtraction(select, arr).join(","));
 }

 /*计算数组差集
 **返回结果数组
 */
 function subtraction(arr1, arr2) {
  var res = [];
  for (var i = 0; i < arr1.length; i++) {
  var flag = true;
  for (var j = 0; j < arr2.length; j++) {
   if (arr2[j] == arr1[i]) {
   flag = false;
   }
  }
  if (flag) {
   res.push(arr1[i]);
  }
  }
  return res;
 }

 /*获取被选父节点的子项目
 **返回结果arr里
 */
 function unitrecursive(t, nodes, arr) {
  for (var i = 0; i < nodes.length; i++) {
  if (!t.tree('isLeaf', nodes[i].target)) {
   var nn = t.tree('getChildren', nodes[i].target);
   for (var j = 0; j < nn.length; j++) {
   arr.push(nn[j].id);
   }
   unitrecursive(t, nn, arr);
  }
  }
 }