Knockout Js 另一个javascript库。 开源, 纯Javascript,小,无依赖,支持众多浏览器。在Asp.net MVC中我们来实现一个简单的级联下拉列表。 先看我们定义的Controller与Model:

    public class HomeController : Controller
    {
        public ActionResult Index()
        {
            ViewBag.Country = new SelectList(Country.GetCountryList(), "Code", "Name");
            return View();
        }
 
        public ActionResult GetStates(string id = "")
        {
            var stateList = State.GetStates()
                .Where(s => s.CountryCode.ToLower() == id.ToLower());
 
            return this.Json(stateList, JsonRequestBehavior.AllowGet);
        }
    }
 
    public class Country
    {
        public string Code { get; set; }
        public string Name { get; set; }
 
        public static List<Country> GetCountryList()
        {
            return new List<Country>
            {
                new Country { Code = "IN", Name = "India" },
                new Country { Code = "US", Name = "United State" },
                new Country { Code = "UK", Name = "United Kingdom" }
            };
        }
    }
 
    public class State
    {
        public string CountryCode { get; set; }
        public int StateId { get; set; }
        public string StateName { get; set; }
 
        public static List<State> GetStates()
        {
            int stateId = 0;
            return new List<State>
            {
                new State { CountryCode = "CN", StateId = stateId++, StateName = "ShangHai" },
                new State { CountryCode = "CN", StateId = stateId++, StateName = "BeiJing" },
                new State { CountryCode = "CN", StateId = stateId++, StateName = "HongKong" },
                new State { CountryCode = "US", StateId = stateId++, StateName = "New York" },
                new State { CountryCode = "US", StateId = stateId++, StateName = "California" },
                new State { CountryCode = "US", StateId = stateId++, StateName = "Washington" },
                new State { CountryCode = "UK", StateId = stateId++, StateName = "London" },
                new State { CountryCode = "UK", StateId = stateId++, StateName = "Scotland" },
                new State { CountryCode = "UK", StateId = stateId++, StateName = "Britian" }
            };
        }
    }


注意这里是为了演示,在MODEL填充的数据。GetStates用于Ajax请求的Action。在前端的cshtml中,类似这样的片段:

<p>
    <b>Select Country :</b> @Html.DropDownList("ddlCountry", ViewBag.Country as SelectList, "Select...", new { onchange = "FetchStates();" })
</p>
<p data-bind="visible: states().length > 0">
    <b>Select State :</b>
    <select data-bind="options: states, optionsText: 'StateName', optionsValue: 'StateId', optionsCaption: 'Choose...'">
    </select>
</p>


上面使用visible的API,从这里可以看出用于控制是否显示。参考官方的Visible Binding 的 API文档。 接着是基于select标签options binding。 在View中Javascript定义我们的ViewModel :

function CascadingDDLViewModel() {
    this.states = ko.observableArray([]);
}
 
var objVM = new CascadingDDLViewModel();
ko.applyBindings(objVM);

 

我们看到上面的代码中,我们创建ko.observableArray类型states属性的ViewModel.knockoutjs中的Observable类型自动通知当它的对象被更新。
这里又借助的data-bind特性,之前文章中有提过它,用knockoutjs的Viewmodel来实现绑定DOM元素行为。无论ViewModel被更新,同时DOM元素也会被自动更新.

function FetchStates() {
    var countryCode = $("#ddlCountry").val();
    $.getJSON("/Home/GetStates/" + countryCode, null, function (data) {
        objVM.states(data);
    });
}


当下拉列表改变时,我们使用jQuery.getJSON方法去获得数据。在请求成功后更新ViewModel,而不需要手动用Javascript做字符串操作来实现一个DropDownList.

您可能感兴趣的文章:

Jquery实现无刷新DropDownList联动
Html 5中自定义data-*特性

 


作者:Petter Liu
出处:http://www.cnblogs.com/wintersun/
本文版权归作者和博客园共有,欢迎转载,但未经作者同意必须保留此段声明,且在文章页面明显位置给出原文连接,否则保留追究法律责任的权利。
该文章也同时发布在我的独立博客中-Petter Liu Blog

posted on 2012-07-09 16:32  PetterLiu  阅读(5606)  评论(0编辑  收藏  举报