MVC 3 Razor视图中的级联下拉

Question

我对如何在Razor视图中实现地址的级联下拉列表感兴趣。我的网站实体有一个SuburbId属性。郊区有CityId，City有ProvinceId。我想在“站点”视图中显示所有郊区，城市和省的下拉列表，例如，郊区下拉列表将首先显示“首先选择一个城市”，以及城市下拉菜单，“首先选择一个省”。在选择省份时，省内的城市都会被填充等。

我怎样才能做到这一点？我从哪里开始？

Answer 1

让我们用一个例子来说明。一如既往的模特开始：

public class MyViewModel
{
    public string SelectedProvinceId { get; set; }
    public string SelectedCityId { get; set; }
    public string SelectedSuburbId { get; set; }
    public IEnumerable<Province> Provinces { get; set; }
}

public class Province
{
    public string Id { get; set; }
    public string Name { get; set; }
}

接下来是控制器：

public class HomeController : Controller
{
    public ActionResult Index()
    {
        var model = new MyViewModel
        {
            // TODO: Fetch those from your repository
            Provinces = Enumerable.Range(1, 10).Select(x => new Province
            {
                Id = (x + 1).ToString(),
                Name = "Province " + x
            })
        };
        return View(model);
    }

    public ActionResult Suburbs(int cityId)
    {
        // TODO: Fetch the suburbs from your repository based on the cityId
        var suburbs = Enumerable.Range(1, 5).Select(x => new
        {
            Id = x,
            Name = "suburb " + x
        });
        return Json(suburbs, JsonRequestBehavior.AllowGet);
    }

    public ActionResult Cities(int provinceId)
    {
        // TODO: Fetch the cities from your repository based on the provinceId
        var cities = Enumerable.Range(1, 5).Select(x => new
        {
            Id = x,
            Name = "city " + x
        });
        return Json(cities, JsonRequestBehavior.AllowGet);
    }
}

最后一个观点：

@model SomeNs.Models.MyViewModel

@{
    ViewBag.Title = "Home Page";
}

<script type="text/javascript" src="/scripts/jquery-1.4.4.js"></script>
<script type="text/javascript">
    $(function () {
        $('#SelectedProvinceId').change(function () {
            var selectedProvinceId = $(this).val();
            $.getJSON('@Url.Action("Cities")', { provinceId: selectedProvinceId }, function (cities) {
                var citiesSelect = $('#SelectedCityId');
                citiesSelect.empty();
                $.each(cities, function (index, city) {
                    citiesSelect.append(
                        $('<option/>')
                            .attr('value', city.Id)
                            .text(city.Name)
                    );
                });
            });
        });

        $('#SelectedCityId').change(function () {
            var selectedCityId = $(this).val();
            $.getJSON('@Url.Action("Suburbs")', { cityId: selectedCityId }, function (suburbs) {
                var suburbsSelect = $('#SelectedSuburbId');
                suburbsSelect.empty();
                $.each(suburbs, function (index, suburb) {
                    suburbsSelect.append(
                        $('<option/>')
                            .attr('value', suburb.Id)
                            .text(suburb.Name)
                    );
                });
            });
        });
    });
</script>

<div>
    Province: 
    @Html.DropDownListFor(x => x.SelectedProvinceId, new SelectList(Model.Provinces, "Id", "Name"))
</div>
<div>
    City: 
    @Html.DropDownListFor(x => x.SelectedCityId, Enumerable.Empty<SelectListItem>())
</div>
<div>
    Suburb: 
    @Html.DropDownListFor(x => x.SelectedSuburbId, Enumerable.Empty<SelectListItem>())
</div>

作为改进，可以通过编写jquery插件来缩短javascript代码，以避免重复某些部分。

---

更新：

谈到一个插件，你可以在一行中找到一些东西：

(function ($) {
    $.fn.cascade = function (options) {
        var defaults = { };
        var opts = $.extend(defaults, options);

        return this.each(function () {
            $(this).change(function () {
                var selectedValue = $(this).val();
                var params = { };
                params[opts.paramName] = selectedValue;
                $.getJSON(opts.url, params, function (items) {
                    opts.childSelect.empty();
                    $.each(items, function (index, item) {
                        opts.childSelect.append(
                            $('<option/>')
                                .attr('value', item.Id)
                                .text(item.Name)
                        );
                    });
                });
            });
        });
    };
})(jQuery);

然后简单地连线：

$(function () {
    $('#SelectedProvinceId').cascade({
        url: '@Url.Action("Cities")',
        paramName: 'provinceId',
        childSelect: $('#SelectedCityId')
    });

    $('#SelectedCityId').cascade({
        url: '@Url.Action("Suburbs")',
        paramName: 'cityId',
        childSelect: $('#SelectedSuburbId')
    });
});

Answer 2

感谢Darin您的解决方案。这对我来说非常有帮助。但正如'xxviktor'提到的那样，我确实得到了循环引用。错误。为了摆脱它，我已经这样做了。

    public string GetCounties(int countryID)
    {
        List<County> objCounties = new List<County>();
        var objResp = _mastRepo.GetCounties(countryID, ref objCounties);
        var objRetC = from c in objCounties
                      select new SelectListItem
                      {
                          Text = c.Name,
                          Value = c.ID.ToString()
                      };
        return new JavaScriptSerializer().Serialize(objRetC);
    }

为了实现自动级联，我以这种方式略微扩展了jQuery扩展。

        $('#ddlCountry').cascade({
            url: '@Url.Action("GetCounties")',
            paramName: 'countryID',
            childSelect: $('#ddlState'),
            childCascade: true
        });

实际的JS使用如下所示的参数（在JSON请求中）。

                // trigger child change
                if (opts.childCascade) {
                    opts.childSelect.change();
                }

希望这有助于有类似问题的人。

Answer 3

请注意，此解决方案无法直接与EF 4.0一起使用。它导致“序列化时检测到循环引用...”错误。以下是可能的解决方案http://blogs.telerik.com/atanaskorchev/posts/10-01-25/resolving_circular_references_when_binding_the_mvc_grid.aspx，我使用了第二个解决方案。

Answer 4

要实现支持MVC内置验证和绑定的级联下拉列表，您需要做一些与此处其他答案中所做的不同的事情。

如果您的模型有验证，这将支持它。来自具有验证的模型的摘录：

[Required]
[DisplayFormat(ConvertEmptyStringToNull = false)]    
public Guid cityId { get; set; }

在您的控制器中，您需要添加一个get方法，以便您的视图能够在以后获取相关数据：

[AcceptVerbs(HttpVerbs.Get)]
public JsonResult GetData(Guid id)
{
    var cityList = (from s in db.City where s.stateId == id select new { cityId = s.cityId, name = s.name }); 
    //simply grabbing all of the cities that are in the selected state 

    return Json(cityList.ToList(), JsonRequestBehavior.AllowGet);  
}

现在，我前面提到过的视图：

在您看来，您有两个类似的下拉列表：

<div class="editor-label">
    @Html.LabelFor(model => model.stateId, "State")
</div>
<div class="editor-field">
    @Html.DropDownList("stateId", String.Empty)
    @Html.ValidationMessageFor(model => model.stateId)
</div>

<div class="editor-label">
    @Html.LabelFor(model => model.cityId, "City")
</div>
<div class="editor-field">
    @*<select id="cityId"></select>*@
    @Html.DropDownList("cityId", String.Empty)
    @Html.ValidationMessageFor(model => model.cityId)
</div>

下拉列表中的内容由控制器绑定，并自动填充。注意：根据我的经验，删除此绑定并依赖java脚本填充下拉列表会使您失去验证。此外，我们在这里绑定的方式与验证很好，所以没有理由改变它。

现在进入我们的jQuery插件：

(function ($) {
$.fn.cascade = function (secondaryDropDown, actionUrl, stringValueToCompare) {
    primaryDropDown = this; //This doesn't necessarily need to be global
    globalOptions = new Array(); //This doesn't necessarily need to be global
    for (var i = 0; i < secondaryDropDown.options.length; i++) {
        globalOptions.push(secondaryDropDown.options[i]);
    }

    $(primaryDropDown).change(function () {
        if ($(primaryDropDown).val() != "") {
            $(secondaryDropDown).prop('disabled', false); //Enable the second dropdown if we have an acceptable value
            $.ajax({
                url: actionUrl,
                type: 'GET',
                cache: false,
                data: { id: $(primaryDropDown).val() },
                success: function (result) {
                    $(secondaryDropDown).empty() //Empty the dropdown so we can re-populate it
                    var dynamicData = new Array();
                    for (count = 0; count < result.length; count++) {
                        dynamicData.push(result[count][stringValueToCompare]);
                    }

                    //allow the empty option so the second dropdown will not look odd when empty
                    dynamicData.push(globalOptions[0].value);
                    for (var i = 0; i < dynamicData.length; i++) {
                        for (var j = 0; j < globalOptions.length; j++) {
                            if (dynamicData[i] == globalOptions[j].value) {
                                $(secondaryDropDown).append(globalOptions[j]);
                                break;
                            }
                        }

                    }
                },
                dataType: 'json',
                error: function () { console.log("Error retrieving cascading dropdown data from " + actionUrl); }
            });
        }
        else {
            $(secondaryDropDown).prop('disabled', true);
        }
        secondaryDropDown.selectedindex = 0; //this prevents a previous selection from sticking
    });
    $(primaryDropDown).change();
};
} (jQuery));

您可以将我创建的上述jQuery复制到视图中的<script>...</script>标记中，或者根据需要复制到单独的脚本文件中（注意我更新了这个以使其跨浏览器，但是我在其中的场景不再需要使用它，它应该工作）。

在相同的脚本标记中（不在单独的文件中），您可以使用以下javascript调用插件：

$(document).ready(function () {
    var primaryDropDown = document.getElementById('stateId');
    var secondaryDropdown = document.getElementById('cityId');
    var actionUrl = '@Url.Action("GetData")'
    $(primaryDropDown).cascade(secondaryDropdown, actionUrl);
});

请记住添加$(document).ready部分，在尝试进行下拉级联之前，页面必须已完全加载。

Answer 5

＆＃13;

＆＃13;

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


<script type="text/javascript">
    $(document).ready(function () {
        //Dropdownlist Selectedchange event
        $("#country").change(function () {
            $("#State").empty();
            $.ajax({
                type: 'POST',
                url: '@Url.Action("State")', // we are calling json method

                dataType: 'json',

                data: { id: $("#country").val() },
                // here we are get value of selected country and passing same value
              

                success: function (states) {
                    // states contains the JSON formatted list
                    // of states passed from the controller

                    $.each(states, function (i, state) {
                        $("#State").append('<option value="' + state.Value + '">' +
                             state.Text + '</option>');
                        // here we are adding option for States

                    });
                },
            error: function (ex) {
                alert('Failed to retrieve states.' + ex);
            }
        });
        return false;
    })
    });
</script>

＆＃13;

<div>
    @Html.DropDownList("country", ViewBag.country as List<SelectListItem>, "CountryName", new { style = "width: 200px;" })
</div>
<div>

</div>
<div>
    @Html.DropDownList("State", ViewBag.country as List<SelectListItem>)

</div>

＆＃13;

＆＃13;

＆＃13;

从控制器我得到值

 public async Task<ActionResult> Country()
    {

        Country co = new Country();
        List<SelectListItem> li = new List<SelectListItem>();
        li.Add(new SelectListItem { Text = "Select", Value = "0" });
        li.Add(new SelectListItem { Text = "India", Value = "1" });
        li.Add(new SelectListItem { Text = "Nepal", Value = "2" });
        li.Add(new SelectListItem { Text = "USA", Value = "3" });
        li.Add(new SelectListItem { Text = "Kenya", Value = "4" }); ;
        ViewBag.country= li;
        return View();
    }
    public JsonResult  state(string id)
    {
        List<SelectListItem> states = new List<SelectListItem>();
        states.Add(new SelectListItem { Text = "--Select State--", Value = "0" });
        switch (id)
        {
            case "1":


                states.Add(new SelectListItem { Text = "MP", Value = "1" });
                states.Add(new SelectListItem { Text = "UP", Value = "2" });
                break;
            case "3":

                states.Add(new SelectListItem { Text = "USA1", Value = "3" });
                states.Add(new SelectListItem { Text = "USA2", Value = "4" });
                break;
        }

        return Json(new SelectList(states, "Value", "Text", JsonRequestBehavior.AllowGet));
    }