<div ng-app="MultiDropDownApp" ng-controller="MultiDropDownControl as vm">
    <label>选择地址:</label>
    <!--ng-options加载所有选择项，ng-model记录当前选择项-->
    <select ng-model="vm.province" ng-options="x.name for x in vm.provinceSort"
            ng-change="vm.selectProvince()" id="" value="" class="form-control width-25">
        <option value="">请选择</option>

    </select>
    <label>—</label>
    <select ng-model="vm.city" ng-options="x.name for x in vm.citySort"
            id="" value="" class="form-control width-25">
        <option value="">请选择</option>

    </select>
</div>

<script src="~/Scripts/angular.min.js"></script>
<script>
    var app = angular.module('MultiDropDownApp', []);
    //可以添加上自己注入的服务
    app.controller('MultiDropDownControl', ['$scope', '$http',
        function ($scope, $http) {
            var vm = this;
            vm.provinceSort = [];
            vm.citySort = [];

            //选择省级单位，初始化市级数据   二级联动
            vm.selectProvince = function () {
                var fatherID = vm.province.id;
                vm.citySort = [];
                $http({
                    method: 'POST',
                    url: '/AngularjsStudy/GetChildrenSort',
                    data: { fatherID: fatherID }
                }).then(function successCallback(data) {
                    vm.citySort = data.data;
                }, function errorCallback(response) {
                    // 请求失败执行代码
                });
            }

            //初始化页面
            function init() {
                //省
                $http({
                    method: 'POST',
                    url: '/AngularjsStudy/GetProvinceSort',
                    data: {}
                }).then(function successCallback(data) {
                    //加载下拉框数据
                    vm.provinceSort = data.data;
                    //设置默认选项
                    vm.province = vm.provinceSort[0];
                }, function errorCallback(response) {
                    // 请求失败执行代码
                });
            }

            //初始化
            init();
        }])
</script>

Controller

        public ActionResult GetProvinceSort()
        {
            List<District> districts = new List<District>();
            districts.Add(new District() {id=1,fatherID=0,name="湖南省" });
            districts.Add(new District() { id =2, fatherID = 0, name = "湖北省" });
            districts.Add(new District() { id =3, fatherID = 0, name = "四川省" });
            return Json(districts);
        }

        public ActionResult GetChildrenSort(int fatherID)
        {
            List<District> districts = new List<District>();
            switch (fatherID)
            {
                case 1:
                    districts.Add(new District() { id = 4, fatherID = 1, name = "长沙市" });
                    districts.Add(new District() { id = 5, fatherID = 1, name = "岳阳市" });
                    districts.Add(new District() { id = 6, fatherID = 1, name = "株洲市" });
                    return Json(districts);
                case 2:
                    districts.Add(new District() { id = 7, fatherID = 2, name = "武汉市" });
                    districts.Add(new District() { id = 8, fatherID = 2, name = "宜昌市" });
                    return Json(districts);
                case 3:
                    districts.Add(new District() { id = 9, fatherID = 3, name = "成都市" });
                    districts.Add(new District() { id = 10, fatherID = 3, name = "遂宁市" });
                    districts.Add(new District() { id = 11, fatherID = 3, name = "巴中市" });
                    districts.Add(new District() { id = 12, fatherID = 3, name = "绵阳市" });
                    districts.Add(new District() { id = 13, fatherID = 3, name = "南充市" });
                    return Json(districts);
                default:
                    districts.Add(new District() { id = 14, fatherID = -1, name = "不知道你选了什么∑q|ﾟДﾟ|p" });
                    return Json(districts);
            }
        }

Model

public class District
{
    public int id { get; set; }
    /// <summary>
    /// 根节点FatherID=0
    /// </summary>
    public int fatherID { get; set; }
    public string name { get; set; }
}