详解ASP.NET MVC之下拉框绑定四种方式

浏览: 14 发布日期: 2016-12-16 分类: asp.net

前言

上两节我们讲了文件上传的问题,关于这个上传的问题还未结束,我也在花时间做做分割大文件处理以及显示进度的问题,到时完成的话再发表,为了不耽误学习MVC其他内容的计划,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:

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,以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持脚本之家。

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