为什么当我填充一个下拉列表本网站HTTP异常情况发生？ [英] Why is this web http exception happening when I am populating a drop down list?

查看：115 发布时间：2016/7/4 20:08:58 c# asp.net-mvc drop-down-menu

本文介绍了为什么当我填充一个下拉列表本网站HTTP异常情况发生？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

型号

联盟和 LeagueDivision 两种模型类

 公共类联赛
{
    公众诠释标识{搞定;组; }
    公共字符串League1 {搞定;组; }
    公共字符串图标{搞定;组; }    公共虚拟的ICollection＆LT; LeagueDivision＆GT; LeagueDivisions {搞定;组; }
}公共类LeagueDivision
{
    公众诠释标识{搞定;组; }
    公众可空＆LT; INT＆GT; LeagueId {搞定;组; }
    公共字符串名称{;组; }
    公共字符串图标{搞定;组; }    公共虚拟联赛{搞定;组; }
}  公共类ViewModelForHostBooster
    {
        [必需（的ErrorMessage =请输入价）]
        [显示（名称=价格）]
        公共十进制价格{搞定;组; }        [必需（的ErrorMessage =请选择一个联赛）]
        [显示（NAME =联盟）]        公众诠释？ SelectedLeague {搞定;组; }
        [必需（的ErrorMessage =请选择一个联赛师）]
        [显示（NAME =联盟分部）]        公众诠释？ SelectedLeagueDivision {搞定;组; }        公众的SelectList LeagueList {搞定;组; }
        公众的SelectList LeagueDivisionList {搞定;组; }
    }

控制器

在 IndexDropdown 行动，我只是填充视图与模型和验证，如果
该模型进行验证，然后填充视图否则返回该视图。在 FetchLeagueDivision 行动，我的基础上传递的参数ID选择Id和模型类的名称属性。

任何人可以指导我为什么 WebHttpException 是当我运行这片code的发生呢？这里是例外 HTTP异常图像

链接

 公共类的DropDownController：控制器
{
    [HTTPGET]
    公众的ActionResult IndexDropDown（）
    {
        ViewModelForHostBooster模式=新ViewModelForHostBooster（）;        ConfigureViewModel（模型）;
        返回查看（模型）;
    }    [HttpPost]
    公众的ActionResult IndexDropDown（ViewModelForHostBooster模型）
    {
        如果（！ModelState.IsValid）
        {
            ConfigureViewModel（模型）;
            返回查看（模型）;
        }        //保存和重定向
        返回RedirectToAction（某处）;
    }
    私人无效ConfigureViewModel（ViewModelForHostBooster模型）
    {
        HostBoostersDBEntities DB =新HostBoostersDBEntities（）;        VAR联赛= db.Leagues.Select（X =＆gt;新建{值= x.Id，文本= x.League1}）了ToList（）;
        model.LeagueList =新的SelectList（联赛，ID，League1）;        如果（model.SelectedLeague.HasValue）
        {
            IEnumerable的＆LT; LeagueDivision＆GT; leaguedivisions = db.LeagueDivisions.Where（L =＆GT; l.LeagueId == model.SelectedLeague.Value）;
            model.LeagueDivisionList =新的SelectList（leaguedivisions，ID，姓名）;
        }
        其他
        {
            model.LeagueDivisionList =新的SelectList（Enumerable.Empty＆LT; SelectListItem＆GT;（））;
        }
    }
}

查看

  @model HostBooster.Models.ViewModelForHostBooster
 @using（Html.BeginForm（））
    {
        ＆LT; DIV＆GT;
            @ Html.LabelFor（M = GT; m.Price）
            @ Html.TextBoxFor（M = GT; m.Price）
            @ Html.ValidationMessageFor（M = GT; m.Price）
        ＆LT; / DIV＆GT;        ＆LT; DIV＆GT;
            @ Html.LabelFor（M = GT; m.SelectedLeague）

异常是发生在这里 @ Html.DropDownListFor（M => m.SelectedLeague，Model.LeagueList）

  @ Html.DropDownListFor（M = GT; m.SelectedLeague，Model.LeagueList）
            @ Html.ValidationMessageFor（M = GT; m.SelectedLeague）
        ＆LT; / DIV＆GT;
        ＆LT; DIV＆GT;
            @ Html.LabelFor（M = GT; m.SelectedLeagueDivision）
            @ Html.DropDownListFor（M = GT; m.SelectedLeagueDivision，Model.LeagueDivisionList）
            @ Html.ValidationMessageFor（M = GT; m.SelectedLeagueDivision）
        ＆LT; / DIV＆GT;
        ＆LT;输入类型=提交值=拯救/＆GT;
    }

解决方案

在视图 Model.LeagueList 为空。它不能为空。
如果编辑视图code像这样（例如），效果很好：

 ＆LT;身体GT;
@using（Html.BeginForm（））
{
    清单＆LT; SelectListItem＆GT;时listItems =新的List＆LT; SelectListItem＆GT;（）;
    listItems.Add（新SelectListItem
    {
        文本=例1
        VALUE =例1
    }）;
    listItems.Add（新SelectListItem
    {
        文本=例2
        VALUE =例2
        选择=真
    }）;
    listItems.Add（新SelectListItem
    {
        文本=例3
        VALUE =例3
    }）;
    ＆LT; DIV＆GT;
        @ Html.LabelFor（M = GT; m.Price）
        @ Html.TextBoxFor（M = GT; m.Price）
        @ Html.ValidationMessageFor（M = GT; m.Price）
    ＆LT; / DIV＆GT;    ＆LT; DIV＆GT;
        @ Html.LabelFor（M = GT; m.SelectedLeague）
        @ Html.DropDownListFor（M = GT; m.SelectedLeague，listItems中）
        @ Html.ValidationMessageFor（M = GT; m.SelectedLeague）
    ＆LT; / DIV＆GT;
    ＆LT; DIV＆GT;
        @ Html.LabelFor（M = GT; m.SelectedLeagueDivision）
        @ Html.DropDownListFor（M = GT; m.SelectedLeagueDivision，Model.LeagueDivisionList）
        @ Html.ValidationMessageFor（M = GT; m.SelectedLeagueDivision）
    ＆LT; / DIV＆GT;
    ＆LT;输入类型=提交值=拯救/＆GT;
}

Model

League and LeagueDivision are two model classes

public class League
{
    public int Id { get; set; }
    public string League1 { get; set; }
    public string Icon { get; set; }

    public virtual ICollection<LeagueDivision> LeagueDivisions { get; set; }
}

public class LeagueDivision
{
    public int Id { get; set; }
    public Nullable<int> LeagueId { get; set; }
    public string Name { get; set; }
    public string Icon { get; set; }

    public virtual League League { get; set; }
} 

  public class ViewModelForHostBooster
    {
        [Required(ErrorMessage = "Please enter price")]
        [Display(Name = "Price")]
        public decimal Price { get; set; }       

        [Required(ErrorMessage = "Please select a league")]
        [Display(Name = "League")]

        public int? SelectedLeague { get; set; }
        [Required(ErrorMessage = "Please select a league division")]
        [Display(Name = "League Division")]

        public int? SelectedLeagueDivision { get; set; }

        public SelectList LeagueList { get; set; }
        public SelectList LeagueDivisionList { get; set; }      


    }

Controller

In IndexDropdown action I am just populating view with model and validating if the model is validated then populate the view otherwise return the view. In FetchLeagueDivision action I am selecting Id and Name properties of model class based on passed argument ID.

Can anybody guide me why a WebHttpException is happening when I run this piece of code? Here is a link of exception Http Exception Image

public class DropDownController : Controller
{
    [HttpGet]
    public ActionResult IndexDropDown()
    {
        ViewModelForHostBooster model = new ViewModelForHostBooster();

        ConfigureViewModel(model);
        return View(model);
    }

    [HttpPost]
    public ActionResult IndexDropDown(ViewModelForHostBooster model)
    {
        if (!ModelState.IsValid)
        {
            ConfigureViewModel(model);
            return View(model);
        }

        // save and redirect
        return RedirectToAction("Somewhere");
    }


    private void ConfigureViewModel(ViewModelForHostBooster model)
    {
        HostBoostersDBEntities db = new HostBoostersDBEntities();

        var leagues = db.Leagues.Select(x => new { Value = x.Id, Text = x.League1 }).ToList();
        model.LeagueList = new SelectList(leagues, "Id", "League1");

        if (model.SelectedLeague.HasValue)
        {
            IEnumerable<LeagueDivision> leaguedivisions = db.LeagueDivisions.Where(l => l.LeagueId == model.SelectedLeague.Value);
            model.LeagueDivisionList = new SelectList(leaguedivisions, "Id", "Name");
        }
        else
        {
            model.LeagueDivisionList = new SelectList(Enumerable.Empty<SelectListItem>());
        }
    }
}

View

@model HostBooster.Models.ViewModelForHostBooster
 @using (Html.BeginForm())
    {
        <div>
            @Html.LabelFor(m => m.Price)
            @Html.TextBoxFor(m => m.Price)
            @Html.ValidationMessageFor(m => m.Price)
        </div>

        <div>
            @Html.LabelFor(m => m.SelectedLeague)

exception is occurring here @Html.DropDownListFor(m => m.SelectedLeague, Model.LeagueList)

            @Html.DropDownListFor(m => m.SelectedLeague, Model.LeagueList)
            @Html.ValidationMessageFor(m => m.SelectedLeague)
        </div>
        <div>
            @Html.LabelFor(m => m.SelectedLeagueDivision)
            @Html.DropDownListFor(m => m.SelectedLeagueDivision, Model.LeagueDivisionList)
            @Html.ValidationMessageFor(m => m.SelectedLeagueDivision)
        </div>
        <input type="submit" value="save" />
    }

解决方案

In view Model.LeagueList is null. It should not be null. if edit view code like this(for example), Works well:

<body>
@using (Html.BeginForm())
{
    List<SelectListItem> listItems = new List<SelectListItem>();
    listItems.Add(new SelectListItem
    {
        Text = "Example1",
        Value = "Example1"
    });
    listItems.Add(new SelectListItem
    {
        Text = "Example2",
        Value = "Example2",
        Selected = true
    });
    listItems.Add(new SelectListItem
    {
        Text = "Example3",
        Value = "Example3"
    });


    <div>
        @Html.LabelFor(m => m.Price)
        @Html.TextBoxFor(m => m.Price)
        @Html.ValidationMessageFor(m => m.Price)
    </div>

    <div>
        @Html.LabelFor(m => m.SelectedLeague)
        @Html.DropDownListFor(m => m.SelectedLeague, listItems)
        @Html.ValidationMessageFor(m => m.SelectedLeague)
    </div>
    <div>
        @Html.LabelFor(m => m.SelectedLeagueDivision)
        @Html.DropDownListFor(m => m.SelectedLeagueDivision, Model.LeagueDivisionList)
        @Html.ValidationMessageFor(m => m.SelectedLeagueDivision)
    </div>
    <input type="submit" value="save" />
}

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为什么当我填充一个下拉列表本网站HTTP异常情况发生？ [英] Why is this web http exception happening when I am populating a drop down list?

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为什么当我填充一个下拉列表本网站HTTP异常情况发生？ [英] Why is this web http exception happening when I am populating a drop down list?

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