ASP.Net MVC DROPDOWNLIST和选择的值 [英] ASP.Net MVC DropdownList and selected value

问题描述

我能够创建一个DropDownList我的MVC项目，但价值没有被选为在DropDownList的选定值。这只是表明全县名单从第一。值是从数据库。我试图从previous后找到它，但它是相当混乱。请给我建议的任何想法。

控制器code

 公众的ActionResult编辑（int i）以
{
     变种项=新的SelectList（db.MST_COUNTRies.ToList（），COUNTRY_ID，COUNTRY_NM）;
     计算机[MST_COUNTRies] =物品;
}
 

查看code

 ＆LT;％= Html.DropDownList（COUNTRY_ID（的SelectList）ViewData的[MST_COUNTRies]）％GT;
 

解决方案

我会使用强类型的视图（不需要的ViewData 和魔术字符串）建议你。与往常一样开始定义您的视图模型类：

 公共类CountriesViewModel
{
    公众诠释？ SelectedCountryId {搞定;组; }
    公共IEnumerable的＆LT; SelectListItem＆GT;国家{搞定;组; }
}
 

然后控制器：

 公共类HomeController的：控制器
{
    公众的ActionResult指数（INT？ID）
    {
        // TODO：从您的数据库获取这些
        VAR国家=新[]
        {
            新{ID = 1，名称=国家1}，
            新{ID = 2，名称=国家2}，
        };        VAR模型=新CountriesViewModel
        {
            国家=新的SelectList（国家，ID，姓名，ID）
        };        返回查看（模型）;
    }
}
 

和最后你的强类型视图：

 ＆LT;％@页面语言=C＃的MasterPageFile =〜/查看/共享/的Site.Master继承=System.Web.Mvc.ViewPage＆LT; SomeNs.Models。 CountriesViewModel＆gt;中％GT;＆LT; ASP：内容ID =内容2ContentPlaceHolderID =日程地址搜索Maincontent=服务器＆GT;    ＆所述;％= Html.DropDownListFor（
            X =＆GT; x.SelectedCountryId，
            Model.Countries，
             -  选择国家  - ）
    ％GT;＆LT; / ASP：内容＆GT;
 

当你调用

现在 /家庭/指数你没有选择的国家，但是，当你通过 ID 来这个动作像 /家庭/指标/ 2 你的国家，这个ID选择。

注：如果您使用的是ASP.NET MVC 1.0，你将不会有强类型DropDownListFor帮手，你可以用这个来代替：

 ＆LT;％= Html.DropDownList（
        SelectedCountryId
        Model.Countries，
         -  选择国家  - ）
％GT;
 

I was able to create a dropdownlist for my MVC project, but the value is not selected as selected value on the dropdownlist. It just shows whole county list from the first.The value is from database. I tried find it from previous post, but it was quite confusing. Please, suggest me for any idea.

Controller Code

public ActionResult Edit(int i)
{
     var items = new SelectList(db.MST_COUNTRies.ToList(), "COUNTRY_ID", "COUNTRY_NM");
     ViewData["MST_COUNTRies"] = items;
}

View Code

<%= Html.DropDownList("COUNTRY_ID", (SelectList)ViewData["MST_COUNTRies"])%>

解决方案

I would suggest you using a strongly typed views (no need of ViewData and magic strings). As always start by defining your view model class:

public class CountriesViewModel
{
    public int? SelectedCountryId { get; set; }
    public IEnumerable<SelectListItem> Countries { get; set; }
}

Then your controller:

public class HomeController : Controller
{
    public ActionResult Index(int? id)
    {
        // TODO: Fetch those from your DB
        var countries = new[] 
        {
            new { Id = 1, Name = "Country 1" },
            new { Id = 2, Name = "Country 2" },
        };

        var model = new CountriesViewModel
        {
            Countries = new SelectList(countries, "Id", "Name", id)
        };

        return View(model);
    }
}

And finally your strongly typed view:

<%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<SomeNs.Models.CountriesViewModel>" %>

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

    <%= Html.DropDownListFor(
            x => x.SelectedCountryId, 
            Model.Countries, 
            "-- Select Country --") 
    %>

</asp:Content>

Now when you call /home/index you get no country selected, but when you pass the id to this action like /home/index/2 you get the country with this id selected.

Remark: If you are using ASP.NET MVC 1.0 you won't have the strongly typed DropDownListFor helper and you could use this instead:

<%= Html.DropDownList(
        "SelectedCountryId", 
        Model.Countries, 
        "-- Select Country --") 
%>

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