<script src="~/Scripts/jquery-1.10.2.js"></script>

 <script src="~/Content/bootstrap/js/bootstrap.js"></script>
 <link href="~/Content/bootstrap/css/bootstrap.css" rel="stylesheet" />

 <script src="~/Content/select2-master/dist/js/select2.js"></script>
 <link href="~/Content/select2-master/dist/css/select2.css" rel="stylesheet" />


　　<select id="sel_menu2" multiple="multiple" class="form-control">
 <optgroup label="系统设置">
 <option value="1">用户管理</option>
 <option value="2">角色管理</option>
 <option value="3">部门管理</option>
 <option value="4">菜单管理</option>
 </optgroup>
 <optgroup label="订单管理">
 <option value="5">订单查询</option>
 <option value="6">订单导入</option>
 <option value="7">订单删除</option>
 <option value="8">订单撤销</option>
 </optgroup>
 <optgroup label="基础数据">
 <option value="9">基础数据维护</option>
 </optgroup>
 </select>

 //多选
 $("#sel_menu2").select2({
 tags: true,
 maximumSelectionLength: 3 //最多能够选择的个数
 });

<select id="sel_menu" class="js-example-templating js-states form-control">
 <optgroup label="系统设置">
  <option value="1">用户管理</option>
  <option value="2">角色管理</option>
  <option value="3">部门管理</option>
  <option value="4">菜单管理</option>
 </optgroup>
 <optgroup label="订单管理">
  <option value="5">订单查询</option>
  <option value="6">订单导入</option>
  <option value="7">订单删除</option>
  <option value="8">订单撤销</option>
 </optgroup>
 <optgroup label="基础数据">
  <option value="9">基础数据维护</option>
 </optgroup>
 </select>



$(function () {
 //带图片
 $("#sel_menu").select2({
 templateResult: formatState,
 templateSelection: formatState
 });
});

function formatState(state) {
 if (!state.id) { return state.text; }
 var $state = $(
 '<span><img src="/content/images/' + state.element.value.toLowerCase() + '.ico" class="img-flag" /> ' + state.text + '</span>'
 );
 return $state;
};

 <select id="sel_menu3" class="js-data-example-ajax form-control">
 <option value="3620194" selected="selected">请选择</option>
 </select>



$(function () {
 //远程筛选
 $("#sel_menu3").select2({
 ajax: {
 url: "/Home/GetProvinces",
 dataType: 'json',
 delay: 250,
 data: function (params) {
 return {
  q: params.term, // search term
  page: params.page
 };
 },
 processResults: function (data, params) {
 params.page = params.page || 1;

 return {
  results: data.items,
  pagination: {
  more: (params.page * 10) < data.total_count
  }
 };
 },
 cache: true
 },
 escapeMarkup: function (markup) { return markup; }, // let our custom formatter work
 minimumInputLength: 1,
 templateResult: formatRepoProvince, // omitted for brevity, see the source of this page
 templateSelection: formatRepoProvince // omitted for brevity, see the source of this page
 });
});



function formatRepoProvince(repo) {
 if (repo.loading) return repo.text;
 var markup = "<div>"+repo.name+"</div>";
 return markup;
}

public List<string> lstProvince = new List<string>() {"北京市","天津市","重庆市","上海市","河北省","山西省","辽宁省","吉林省","黑龙江省","江苏省","浙江省","安徽省","福建省","江西省","山东省","河南省","湖北省","湖南省","广东省","海南省","四川省","贵州省","云南省","陕西省","甘肃省","青海省","台湾省","内蒙古自治区","广西壮族自治区","西藏自治区","宁夏回族自治区","新疆维吾尔自治区","香港特别行政区","澳门特别行政区" };
 public JsonResult GetProvinces(string q, string page)
 {
 var lstRes = new List<Province>();
 for (var i = 0; i < 30; i++)
 {
 var oProvince = new Province();
 oProvince.id = i;
 oProvince.name = lstProvince[i];
 lstRes.Add(oProvince);
 }
 if (!string.IsNullOrEmpty(q.Trim()))
 {
 lstRes = lstRes.Where(x => x.name.Contains(q)).ToList();
 }
 var lstCurPageRes = string.IsNullOrEmpty(page) ? lstRes.Take(10) : lstRes.Skip(Convert.ToInt32(page) * 10 - 10).Take(10);
 return Json(new { items = lstCurPageRes, total_count = lstRes.Count }, JsonRequestBehavior.AllowGet);
 }

 var oMenuIcon = $("#txt_menuicon_web").select2({
 placeholder: "请选择菜单图标",
 templateResult: oInit.formatState,
 templateSelection: oInit.formatState
 });
oMenuIcon.val();

 var oMenuIcon = $("#txt_menuicon_web").select2({
 placeholder: "请选择菜单图标",
 templateResult: oInit.formatState,
 templateSelection: oInit.formatState
 });
 oMenuIcon.val("CA").trigger("change");