通用的下拉联动封装(级联)

前言

平时工作中下拉联动是相对比较麻烦的地方，虽然逻辑简单，但是需要写一堆js跟ajax请求。现在打算在.net core  mvc下封装一个下拉联动组件方便使用。

下面将实现一个 国家 语言 省市区 的多级联动

创建实体模型

  1     public class UserModel
    {
        /// <summary>
        /// 用户名
        /// </summary>
        public string UserName { get; set; }


        /// <summary>
        /// 国家
        /// </summary>
        public int CountryId { get; set; }

        /// <summary>
        /// 语言
        /// </summary>
        public int LanguageId { get; set; }

        /// <summary>
        ///省
        /// </summary>
        public int PronviceId { get; set; }

        /// <summary>
        /// 市
        /// </summary>
        public int CityId { get; set; }

        /// <summary>
        /// 区
        /// </summary>
        public int GetDistrictId { get; set; }

    }

    public class Area
    {
        public int Id { get; set; }

        public string Name { get; set; }

        public int? ParentId { get; set; }
    }

    public class Language
    {
        public int Id { get; set; }

        public int CountryId { get; set; }

        public string Name { get; set; }
    }

写出对应下拉的Action方法

这里  下拉contorler名称约定为DropdownListController,Action名称约定为  Get +字段名的方式,参数名称约定使用 父级字段的名称。这样在前台页面就不用指定获取数据源的url了

  public class DropdownListController : Controller
    {
        private List<Area> areas;

        private List<Language> languages;

        public DropdownListController()
        {
            areas = new List<Area>
            {
                new Area { Id = 1, Name = "中国", ParentId = null },
                new Area { Id = 2, Name = "美国", ParentId = null },
                new Area { Id = 3, Name = "江苏省", ParentId = 1 },
                new Area { Id = 4, Name = "浙江省", ParentId = 1 },
                new Area { Id = 5, Name = "纽约州", ParentId = 2 },
                new Area { Id = 6, Name = "南京市", ParentId = 3 },
                new Area { Id = 7, Name = "杭州市", ParentId = 4 },
                new Area { Id = 8, Name = "纽约市", ParentId = 5 },
                new Area { Id = 9, Name = "曼哈顿区", ParentId = 8 },
                new Area { Id = 10, Name = "老庙区", ParentId = 6 },
                new Area { Id = 11, Name = "西湖区", ParentId = 7 }
            };

            languages = new List<Language>
            {
                new Language{ Id=1,CountryId=1, Name="简体中文" },
                new Language{ Id=2,CountryId=2, Name="美式英语"},
            };
        }

        public IActionResult GetCountryId()
        {
            return Json(areas.FindAll(x => x.ParentId == null).Select(x => new { value = x.Id, text = x.Name }));
        }

        public IActionResult GetLanguageId(int countryId)
        {
            return Json(languages.FindAll(x => x.CountryId == countryId).Select(x => new { value = x.Id, text = x.Name }));
        }

        public IActionResult GetPronviceId(int countryId)
        {
            return Json(areas.FindAll(x => x.ParentId == countryId).Select(x => new { value = x.Id, text = x.Name }));
        }

        public IActionResult GetCityId(int pronviceId)
        {
            return Json(areas.FindAll(x => x.ParentId == pronviceId).Select(x => new { value = x.Id, text = x.Name }));
        }

        public IActionResult GetDistrictId(int cityId)
        {
            return Json(areas.FindAll(x => x.ParentId == cityId).Select(x => new { value = x.Id, text = x.Name }));
        }
    }

前台Html

引用了 bootstrap, jquery

@model UserModel

 <a asp-action="Edit" class="btn btn-success m-b-15">去编辑页</a>
<div class="form-inline row">
    <div class="form-group ">
        <label>国家</label>
        <select asp-for="CountryId" class="form-control" asp-items="ViewBag.CountryList"
                data-select-childids="LanguageId,PronviceId">
            <option value="">请选择</option>
        </select>
    </div>
    <div class="form-group ">
        <label>语言</label>
        <select asp-for="LanguageId" class="form-control">
            <option value="">请选择</option>
        </select>
    </div>
    <div class="form-group">
        <label>省</label>
        <select asp-for="PronviceId" class="form-control" data-select-childids="CityId">
         <option value="">请选择</option>
        </select>
    </div>
    <div class="form-group">
        <label>市</label>
        <select asp-for="CityId" class="form-control"   data-select-childids="DistrictId">
            <option value="">请选择</option>
        </select>
    </div>
    <div class="form-group">
        <label>区</label>
        <select asp-for="DistrictId" class="form-control">
            <option value="">请选择</option>
        </select>
    </div>
</div>

下拉联动的js,基于 jquery

$(function () {
    //下拉联动初始化
    $('select[data-select-childids]').each(function () {
        getChildSelect($(this).attr("id"), true);
    });

    //下拉联动  data-select-childids 填写联动的Id,data-select-url 数据请求路径,data-select-paramids 追加的参数,data-select-value 当前值
    $('select[data-select-childids]').change(function (e) {
        getChildSelect($(this).attr("id"));
    });

    //清空下拉联动子选择项
    function getChildSelect(selectid, isInit) {
        var select = $('#' + selectid);

        var selectchildIds = select.data('select-childids');
        if (!selectchildIds) return;
        var childIds = selectchildIds.split(',')

        for (var i = 0; i < childIds.length; i++) {
            if (!childIds[i]) continue;

            var child = $('#' + childIds[i]);
            var childValue = child.val();
            if (!childValue)
                childValue = child.data("select-value");

            child.empty();

            //默认值设定
            var hasdefault = child.data("select-hasdefault");
            if (hasdefault != "false") {
                child.append('<option value="">请选择</option>');
            }

            //父级下拉有值时，ajax获取数据
            if (select.val()) {var url = child.data('select-url') ? child.data('select-url') : '/DropdownList/Get' + child.attr("id");//url默认值
                var verb = child.data('verb') ? child.data('verb') : 'GET';//请求的方法

                var paramObj = {};//追加参数
                getParentSelectParam(selectid, paramObj)

                //追加控制参数
                var paramids = child.data('select-paramids');
                if (paramids) {
                    var paramidsArr = paramids.split(',')
                    for (var k = 0; k < paramidsArr.length; k++) {
                        paramObj[paramidsArr[k]] = $('#' + paramidsArr[k]).val();
                    }
                }

                $.ajax({
                    type: verb, url: url, data: paramObj, async: false,
                    contentype: "application/x-www-form-urlencoded; charset=UTF-8",
                    success: function (data) {
                        if (data) {
                            for (var j = 0; j < data.length; j++) {
                                var selected = data[j].value == childValue ? 'selected = "selected"' : '';
                                child.append('<option value="' + data[j].value + '" ' + selected + '>' + data[j].text + '</option>');
                            }
                        }
                    }
                });
            }

            //子级下拉如果还有下级,非初始化的时候 递归
            if (!isInit && child.data('select-childids'))
                getChildSelect(child.attr("id"));

        }
    }

    //递归获取父级选中的值 param追加的url参数
    function getParentSelectParam(selectid, param) {
        var select = $("#" + selectid);
        param[selectid] = $(select).val();

        $('select[data-select-childids]').each(function () {
            var id = $(this).attr("id");
            if (selectid != id) {
                var childids = $(this).data('select-childids');
                if (childids) {
                    childidsArr = childids.split(',');
                    for (var i = 0; i < childidsArr.length; i++) {
                        if (childidsArr[i] == selectid) {
                            getParentSelectParam(id, param);//继续向父级查找
                        }
                    }
                }
            }
        });
    }
});

后台 action

 public class HomeController : Controller
    {
        private List<Area> areas;

        public HomeController()
        {
            areas = new List<Area>
            {
                new Area { Id = 1, Name = "中国", ParentId = null },
                new Area { Id = 2, Name = "美国", ParentId = null },
                new Area { Id = 3, Name = "江苏省", ParentId = 1 },
                new Area { Id = 4, Name = "浙江省", ParentId = 1 },
                new Area { Id = 5, Name = "纽约州", ParentId = 2 },
                new Area { Id = 6, Name = "南京市", ParentId = 3 },
                new Area { Id = 7, Name = "杭州市", ParentId = 4 },
                new Area { Id = 8, Name = "纽约市", ParentId = 5 },
                new Area { Id = 9, Name = "曼哈顿区", ParentId = 8 },
                new Area { Id = 10, Name = "老庙区", ParentId = 6 },
                new Area { Id = 11, Name = "西湖区", ParentId = 7 }
            };
        }

        public IActionResult Index()
        {
            ViewBag.CountryList = areas.FindAll(x => x.ParentId == null).Select(x =>
                                                                         new SelectListItem
                                                                         {
                                                                             Value = x.Id.ToString(),
                                                                             Text = x.Name
                                                                         });

            return View(new UserModel());
        }

        public IActionResult Edit()
        {
            ViewBag.CountryList = areas.FindAll(x => x.ParentId == null).Select(x =>
                                                                         new SelectListItem
                                                                         {
                                                                             Value = x.Id.ToString(),
                                                                             Text = x.Name
                                                                         });

            return View(new UserModel() { CountryId = 2, PronviceId = 5, CityId=8,DistrictId = 9, LanguageId = 2 });
        }
    }

运行效果

用法说明

<a asp-action="Index" class="btn btn-success m-b-15">返回</a>
<br /><br />
<div class="form-inline row">
    <div class="form-group ">
        <label>国家</label>
        <select asp-for="CountryId" class="form-control selectList" asp-items="ViewBag.CountryList"
                data-select-childids="LanguageId,PronviceId">
            <option value="">请选择</option>
        </select>
    </div>
    <div class="form-group ">
        <label>语言</label>
        <select asp-for="LanguageId" class="form-control"
                data-select-value="@Model.LanguageId"  
                data-select-url="/DropDownList/GetLanguageId?id=1" 
                data-select-paramids="CountryId"  
                data-select-hasdefault="false" 
                data-verb="Get" 请求的方式
                >
            <option value="">请选择</option>
        </select>
    </div>
    <div class="form-group">
        <label>省</label>
        <select asp-for="PronviceId" class="form-control"
                data-select-childids="CityId"
                data-select-value="@Model.PronviceId"
                data-select-url="/DropDownList/GetPronviceId?id=1"
                data-select-paramids="CountryId"
                >
            <option value="">请选择</option>
        </select>
    </div>
    <div class="form-group">
        <label>市</label>
        <select asp-for="CityId" class="form-control"
                data-select-childids="DistrictId"
                data-select-value="@Model.CityId"
                data-select-url="/DropDownList/GetCityId"
                data-select-paramids="PronviceId"
                >
            <option value="">请选择</option>
        </select>
    </div>
    <div class="form-group">
        <label>区</label>
        <select asp-for="DistrictId" class="form-control"
                data-select-value="@Model.DistrictId"
                data-select-url="/DropDownList/GetDistrictId"
                >
            <option value="">请选择</option>
        </select>
    </div>
</div>

   data-select-childids ：设置联动的select下拉的Id逗号分隔。例如在国家的下拉中 data-select-childids="LanguageId,PronviceId"表示，国家的下拉影响 语言和 省

   data-select-value:   数据加载时的初始值 用在编辑表单时,存储当前下拉

   data-select-url: 请求的url

   data-select-paramids: 参数值的Id