角度级联下拉菜单，它们之间有关键关系答案

【问题标题】：cascading dropdown in angular with key relation between them角度级联下拉菜单，它们之间有关键关系
【发布时间】：2016-10-26 15:25:33
【问题描述】：

我有国家和州dropdowns.Country 和州有关系countryid。

我在为这两个级联下拉菜单获取数据时遇到错误。

以下是控制器返回国家/地区的 JsonResult 时出错的图像。

角函数：

var getdata = fac.GetCountry = function () {
     return $http.get('/Data/GetCountries')
 };
 getdata.then(function (d) {
     $scope.CountryList = d.data;
 }, function (error) {
     alert('Error!');
 });

控制器：

public JsonResult GetCountries()
{
    List<Country> allCountry = new List<Country>();
    using (SunilEntities dc = new SunilEntities())
    {
        allCountry = dc.Countries.OrderBy(a => a.CountryName).ToList();
    }
    return new JsonResult { Data = allCountry, JsonRequestBehavior = JsonRequestBehavior.AllowGet };
    //return Json(allCountry, JsonRequestBehavior.AllowGet);
}

查看：

<div ng-controller="dropdowns">
    Country : <select ng-model="CountryID" ng-options="I.CountryID as I.CountryName for I in CountryList" ng-change="GetState()">
                <option value="">Select Country</option>
              </select>
    State : <select ng-model="StateID" ng-options="I.StateID as I.StateName for I in StateList">
                <option value="">{{StateTextToShow}}</option>
            </select>
    <input type="button" value="Get Selected Values" ng-click="ShowResult()"/>
    <div style="padding:10px; font-weight:bold; border:1px solid #f3f3f3">
        {{Result}}
    </div>
</div>

型号：

public partial class Country
{
    public Country()
    {
        this.States = new HashSet<State>();
    }

    public int CountryID { get; set; }
    public string CountryName { get; set; }

    public virtual ICollection<State> States { get; set; }
}

public partial class State
{
    public int StateID { get; set; }
    public string StateName { get; set; }
    public Nullable<int> CountryID { get; set; }

    public virtual Country Country { get; set; }
    public virtual State State1 { get; set; }
    public virtual State State2 { get; set; }
}

public DbSet<Country> Countries { get; set; }
public DbSet<State> States { get; set; }

【问题讨论】：

标签： angularjs entity-framework model-view-controller

【解决方案1】：

我得到了解决方案。

通过稍微改变操作（控制器）我得到了结果。

控制器：-

        public JsonResult GetCountries()
        {         
            using (SunilEntities dc = new SunilEntities())
            {
                var ret = dc.Countries.Select(x => new { x.CountryID, x.CountryName }).ToList();
                return Json(ret, JsonRequestBehavior.AllowGet);            

            }            
        }

        // Fetch State by Country ID
        public JsonResult GetStates(int countryID)
        {             
            using (SunilEntities dc = new SunilEntities())
            {                  
                var ret = dc.States.Where(x => x.CountryID == countryID).Select(x => new { x.StateID, x.StateName }).ToList();
                return Json(ret, JsonRequestBehavior.AllowGet);
            }              
        }

我有国家和州的下拉菜单。国家和州在 coutryid 上有关系。

我在获取这两个级联下拉列表的数据时遇到错误。

以下是控制器返回国家/地区的 JsonResult 时出错的图像。

角函数：-

   var getdata=  fac.GetCountry = function () {
        return $http.get('/Data/GetCountries')
    };
    getdata.then(function (d) {
        $scope.CountryList = d.data;
    }, function (error) {
        alert('Error!');
    });

查看：-

<div ng-controller="dropdowns">
    Country : <select ng-model="CountryID" ng-options="I.CountryID as I.CountryName for I in CountryList" ng-change="GetState()">
                <option value="">Select Country</option>
              </select>
    State : <select ng-model="StateID" ng-options="I.StateID as I.StateName for I in StateList">
                <option value="">{{StateTextToShow}}</option>
            </select>
    <input type="button" value="Get Selected Values" ng-click="ShowResult()"/>
    <div style="padding:10px; font-weight:bold; border:1px solid #f3f3f3">
        {{Result}}
    </div>
</div>

型号：-

public partial class Country
    {
        public Country()
        {
            this.States = new HashSet<State>();
        }

        public int CountryID { get; set; }
        public string CountryName { get; set; }

        public virtual ICollection<State> States { get; set; }
    }

   public partial class State
    {
        public int StateID { get; set; }
        public string StateName { get; set; }
        public Nullable<int> CountryID { get; set; }

        public virtual Country Country { get; set; }
        public virtual State State1 { get; set; }
        public virtual State State2 { get; set; }
    }

   public DbSet<Country> Countries { get; set; }
   public DbSet<State> States { get; set; }

【讨论】：