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ASP.NET MVC 下拉列表实现

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:

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

    }

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绑定ViewBag传值:

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//从数据库中读取
var categoryList = new List() {
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() {
new SelectListItem(){Value="0",Text="全部",Selected=true}
};
var selectList = new SelectList(categoryList, "CategoryId", "CategoryName");
selectItemList.AddRange(selectList);
ViewBag.database = selectItemList;
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视图稍加修改:

@Html.DropDownList("database-dropdownlist", ViewBag.database as IEnumerable, 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”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:

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public enum Language
{
Chinese,
English,
Japan,
Spanish,
Urdu
}
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获取枚举值并绑定:

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

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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
}
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在视图中进行绑定:

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@Html.LabelFor(model => model.Language, htmlAttributes: new { @class = "control-label col-md-2" })

@Html.EnumDropDownListFor(model => model.Language, htmlAttributes: new { @class = "form-control" })
@Html.ValidationMessageFor(model => model.Language, "", new { @class = "text-danger" })


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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。

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

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(2)初始化数据

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List provinceList = new List() {
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"}
};
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以及绑定ViewBag到下拉框和控制器上的方法:

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[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);
    }

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(3)视图展示

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@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" })




@Html.LabelFor(m => m.City, new { @class = "control-label col-md-2" })

@Html.DropDownListFor(m => m.City,
new SelectList(Enumerable.Empty(), "CityId", "CityName"),
"选择所在市",
new { @class = "form-control" })
@Html.ValidationMessageFor(m => m.City, "", new { @class = "text-danger" })



@Html.LabelFor(m => m.ZipCode, htmlAttributes: new { @class = "control-label col-md-2" })

@Html.TextBoxFor(m => m.ZipCode, new { @class = "form-control" })
@Html.ValidationMessageFor(m => m.ZipCode, "", new { @class = "text-danger" })



@Html.LabelFor(m => m.Phone, new { @class = "control-label col-md-2" })

@Html.TextBoxFor(m => m.Phone, new { @class = "form-control" })
@Html.ValidationMessageFor(m => m.Phone, "", new { @class = "text-danger" })




}
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(4)根据省下拉框选择到市下拉框脚本

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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(
$('').val(city.CityId).html(city.CityName));
});
}
});
}
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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:)。

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