MVC 绑定 下拉框数据

HTML:

<div class="form-group col-sm-12">
                        <div class="col-sm-4">
                            <label for="GroupId" class="control-label">分组名称</label>
                        </div>
                        <div class="col-sm-8">
                            @Html.DropDownList("GroupId", ViewBag.database as IEnumerable<SelectListItem>, new { @class = "form-control" })
                        </div>
                    </div>

CS :

   /// <summary>
        /// 这是子页面
        /// </summary>
        /// <returns></returns>
        public ActionResult Edit()
        {
            //----查询 分组 数据列表 开始----
            int Page = Convert.ToInt32(string.IsNullOrWhiteSpace(Request["page"]) ? "" : Request["page"]);
            int limit = Convert.ToInt32(string.IsNullOrWhiteSpace(Request["limit"]) ? "" : Request["limit"]);

            Group Group = new Group();

            Group.GroupId = Convert.ToInt32(string.IsNullOrWhiteSpace(Request["GroupId"]) ? "" : Request["GroupId"]);
            Group.GroupCode = string.IsNullOrWhiteSpace(Request["GroupCode"]) ? "" : Request["GroupCode"];
            Group.GroupName = string.IsNullOrWhiteSpace(Request["GroupName"]) ? "" : Request["GroupName"];

            JsonResultDapper jrd = GroupManager.SelectGroupList(Group, Page, limit);

            //----查询 分组 数据列表 结束----

            var selectItemList = new List<SelectListItem>() {
                new SelectListItem(){ Value="", Text="--全部--", Selected=true }
            };

            IEnumerable<object> list = jrd.rows as IEnumerable<object>;
            var GroupList = new SelectList(list, "GroupId", "GroupName");

            selectItemList.AddRange(GroupList);
            ViewBag.database = selectItemList;

            return PartialView();
        }