ASP.NET MVC 下拉列表实现

https://blog.csdn.net/Ryan_laojiang/article/details/75349555?locationNum=10&fps=1

前言

我们今天开始好好讲讲关于MVC中下拉框中绑定枚举的几种方式。

话题引入

一般在下拉框中绑定数据的话，分为几种情况。

（1）下拉框中的数据是写死的，我们直接给出死代码即可。

（2）下拉框中的数据从数据库中读取出来，从而进行显示。

（3）下拉框中直接用枚举显示。

（4）下拉框中一个选择的值改变另外一个下拉框中的值。

关于下拉框中绑定大概就是以上四种方式，接下来我们一一来破解，我们样式利用Bootstrap来表示，顺便也温习温习Bootstrap。

下拉框硬编码【一】

我们在控制器中给出如下数据并利用ViewBag来进行传递

           ViewBag.hard_value = new List<SelectListItem>() {
                new SelectListItem(){Value="0",Text="xpy0928"},
                new SelectListItem(){Value="1",Text="cnblogs"}
            };

在数据中进行如下绑定

  @Html.DropDownList("hard-code-dropdownlist", new SelectList(ViewBag.hard_value, "Value", "Text"), new { @class = "btn btn-success dropdown-toggle form-control" })

下面我们来看看效果：

下拉框读取数据库【二】

这个要读取数据库，我们就给出一个类测试就ok，并给出默认选中值，测试类：

        public class BlogCategory
        {
            public int CategoryId { get; set; }
            public string CategoryName { get; set; }

        }

绑定ViewBag传值：

            //从数据库中读取
            var categoryList = new List<BlogCategory>() {
                new BlogCategory(){CategoryId=1,CategoryName="C#"},
                new BlogCategory(){CategoryId=2,CategoryName="Java"},
                new BlogCategory(){CategoryId=3,CategoryName="JavaScript"},
                new BlogCategory(){CategoryId=4,CategoryName="C"}
            };
            var selectItemList = new List<SelectListItem>() {
                new SelectListItem(){Value="0",Text="全部",Selected=true}
            };
            var selectList = new SelectList(categoryList, "CategoryId", "CategoryName");
            selectItemList.AddRange(selectList);
            ViewBag.database = selectItemList;

视图稍加修改：

@Html.DropDownList("database-dropdownlist", ViewBag.database as IEnumerable<SelectListItem>, new { @class = "btn btn-success dropdown-toggle form-control" })

看看效果：

注意：上述视图中 ViewBag.database 需要进行转换否则出现如下错误：

 CS1973: “System.Web.Mvc.HtmlHelper<dynamic>”没有名为“DropDownList”的适用方法，但似乎有一个具有该名称的扩展方法。扩展方法不能进行动态调度。请考虑强制转换动态参数，或调用该扩展方法但不使用扩展方法语法。

下拉框绑定枚举【三】（一）

我们同样给出一个测试类：

        public enum Language
        {
            Chinese,
            English,
            Japan,
            Spanish,
            Urdu
        }

获取枚举值并绑定：

 ViewBag.from_enum = Enum.GetValues(typeof(Language)).Cast<Language>();

视图给出：

  @Html.DropDownList("database-dropdownlist", new SelectList(ViewBag.from_enum), new { @class = "btn btn-success dropdown-toggle form-control" })

继续看看成果：

下拉框绑定枚举【三】（二）

利用扩展方法  @Html.EnumDropDownListFor 来实现。接下来依次给出两个类来进行演示：

    public class StudentModel
    {
        [Display(Name = "语言")]
        public ProgrammingLanguages Language { get; set; }
    }

    public enum ProgrammingLanguages
    {
        [Display(Name = "ASP.NET")]
        ASPNet,
        [Display(Name = "C# .NET")]
        CSharp,
        [Display(Name = "Java")]
        Java,
        [Display(Name = "Objective C")]
        ObjectiveC,
        [Display(Name = "Visual Basic .NET")]
        VBNet,
        [Display(Name = "Visual DataFlex")]
        VisualDataFlex,
        [Display(Name = "Visual Fortran")]
        VisualFortran,
        [Display(Name = "Visual FoxPro")]
        VisualFoxPro,
        [Display(Name = "Visual J++")]
        VisualJPlus
    }

在视图中进行绑定：

   <div class="form-group">
        @Html.LabelFor(model => model.Language, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EnumDropDownListFor(model => model.Language, htmlAttributes: new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.Language, "", new { @class = "text-danger" })
        </div>
    </div>

我们看看结果：

下拉框选择则另一个下拉框对应改变 【四】

此例最合适的例子莫过于省市选择的案例。我们一起来看看。

（1）所属省、市一级雇员类。

    public class Province
    {
        public int provinceId { get; set; }
        public string provinceName { get; set; }
        public string Abbr { get; set; }
    }

    public class City
    {
        public int CityId { get; set; }
        public string CityName { get; set; }
        public int provinceId { get; set; }
    }

    public class Employees
    {

        [Key]
        public int EmployeeId { get; set; }

        [Required, Display(Name = "雇员名字")]
        public string EmployeeName { get; set; }

        [Required, Display(Name = "地址")]
        public String Address { get; set; }

        [Required, Display(Name = "所属省")]
        public int Province { get; set; }

        [Required, Display(Name = "所在城市")]
        public int City { get; set; }

        [Display(Name = "地区代码")]
        public String ZipCode { get; set; }

        [Required, Display(Name = "联系号码")]
        public String Phone { get; set; }
    }

（2）初始化数据

 List<Province> provinceList = new List<Province>() {
                new Province(){provinceId=1,provinceName="湖南",Abbr="hunan_province"},
                new Province(){provinceId=2,provinceName="广东",Abbr="guangdong_province"},
                new Province(){provinceId=3,provinceName="吉林",Abbr="jilin_province"},
                new Province(){provinceId=4,provinceName="黑龙江",Abbr="heilongjiang_province"}
            };

以及绑定ViewBag到下拉框和控制器上的方法：

        [HttpGet]
        public ActionResult Create()
        {

            ViewBag.ProvinceList = provinceList;
            var model = new Employees();
            return View(model);
        }

        [HttpPost]
        public ActionResult Create(Employees model)
        {
            if (ModelState.IsValid)
            {

            }
            ViewBag.ProvinceList = provinceList;
            return View(model);
        }

        public ActionResult FillCity(int provinceId)
        {
            var cities = new List<City>() {
             new City(){CityId=10,CityName="岳阳市",provinceId=1},
             new City(){CityId=10,CityName="深圳市",provinceId=2},
             new City(){CityId=10,CityName="吉林市",provinceId=3},
             new City(){CityId=10,CityName="哈尔滨市",provinceId=4}
            };
            cities = cities.Where(s => s.provinceId == provinceId).ToList();
            return Json(cities, JsonRequestBehavior.AllowGet);
        }

（3）视图展示

    @using (Html.BeginForm())
    {
        @Html.AntiForgeryToken()

        <div class="form-horizontal">
            <h4>注册雇员</h4>
            <div class="form-group">
                @Html.LabelFor(m => m.EmployeeName, new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.TextBoxFor(m => m.EmployeeName, new { @class = "form-control" })
                    @Html.ValidationMessageFor(m => m.EmployeeName, "", new { @class = "text-danger" })
                </div>
            </div>
            <div class="form-group">
                @Html.LabelFor(m => m.Address, new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.TextBoxFor(m => m.Address, new { @class = "form-control" })
                    @Html.ValidationMessageFor(m => m.Address, "", new { @class = "text-danger" })
                </div>
            </div>
            <div class="form-group">
                @Html.LabelFor(m => m.Province, new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.DropDownListFor(m => m.Province,
new SelectList(ViewBag.ProvinceList, "provinceId", "provinceName"),
                  "选择所在省",
                  new { @class = "form-control", @onchange = "FillCity()" })
                    @Html.ValidationMessageFor(m => m.Province, "", new { @class = "text-danger" })
                </div>
            </div>
            <div class="form-group">
                @Html.LabelFor(m => m.City, new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.DropDownListFor(m => m.City,
           new SelectList(Enumerable.Empty<SelectListItem>(), "CityId", "CityName"),
                  "选择所在市",
                  new { @class = "form-control" })
                    @Html.ValidationMessageFor(m => m.City, "", new { @class = "text-danger" })
                </div>
            </div>
            <div class="form-group">
                @Html.LabelFor(m => m.ZipCode, htmlAttributes: new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.TextBoxFor(m => m.ZipCode, new { @class = "form-control" })
                    @Html.ValidationMessageFor(m => m.ZipCode, "", new { @class = "text-danger" })
                </div>
            </div>
            <div class="form-group">
                @Html.LabelFor(m => m.Phone, new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.TextBoxFor(m => m.Phone, new { @class = "form-control" })
                    @Html.ValidationMessageFor(m => m.Phone, "", new { @class = "text-danger" })
                </div>
            </div>
            <div class="form-group">
                <div class="col-md-offset-2 col-md-10">
                    <input type="submit" value="Create" class="btn btn-success" />
                    <a href="/Home/Employees" class="btn btn-warning">Cancel</a>
                </div>
            </div>
        </div>
    }

（4）根据省下拉框选择到市下拉框脚本

       function FillCity() {
            var provinceId = $('#Province').val();
            $.ajax({
                url: '/Home/FillCity',
                type: "GET",
                dataType: "JSON",
                data: { provinceId: provinceId },
                success: function (cities) {
                    $("#City").html("");
                    $.each(cities, function (i, city) {
                        $("#City").append(
                            $('<option></option>').val(city.CityId).html(city.CityName));
                    });
                }
            });
        }

我们来看看整个过程：

结语

对于下拉框绑定基本上已全部囊括进去，不断钻研，不断总结才能有能力上更好的提升。希望对阅读本文的你有所帮助，如果有帮助，不妨讨打（乞讨打赏）一下，1块也是爱:)。