Mvc razor dropdownlist html helper重置选定的值 [英] Mvc razor dropdownlist html helper resets selected value

问题描述

这个让我摸不着头脑，因为我还是MVC和Razor的新手。我正在动态构建一些选择项目列表，其中有一个项目是预选的，没有大问题。得到的是，在将列表传递给Html帮助函数后，所选项目将被取消选择，列表默认为第一项。单步执行页面加载，List< SelectListItem>在进入辅助函数之前具有正确的值。我不使用实体框架进行数据库操作。

This one has got me scratching my head as I'm still pretty new to MVC and Razor. I'm building a couple of Select Item lists dynamically that have one item pre-selected, no biggie. What is getting me is that after the list is passed into the Html helper function, the selected item is being de-selected and the list defaults to the first item. Stepping through the page load, the List<SelectListItem> has the correct values prior to entering the helper function. I'm NOT using the Entity Framework for database operations.

<td>
  @{
    List<SelectListItem> itemList = Functions.GetListForProperty(property);
  }
  <% Correct value is selected in the list %>
  @Html.DropDownList("PropertyList", itemList)
  <% Selected = false for the previously selected item, wtf? %>
</td>

我在这里缺少一些设置。视图是使用脚手架构建的，但我有其他视图，动态生成的下拉列表不会这样做。



我尝试过：



我尝试了两种辅助函数，@ Html.DropDownListFor（Model => model.property，IEnumerable< SelectListItem>）和@ Html.DropDownList（Name，IEnumerable< SelectListItem>）并得到相同的结果。我甚至已经内联了构建列表的代码并且仍然得到了相同的东西。

Is there some setting I'm missing here. The view is built with the scaffolding but I have other views with dynamically generated drop down lists that don't behave this way.

What I have tried:

I've tried both flavors of the helper function, @Html.DropDownListFor(Model => model.property, IEnumerable<SelectListItem>) and @Html.DropDownList("Name", IEnumerable<SelectListItem>) and get the same results. I have even inlined the code that builds the list and still get the same thing.

推荐答案

找出我的问题。事实证明是非常简单的事情。问题在于视图包。



@ Html.DropDownListFor（Model => Model.Property，selectList）的问题是Model.Property不是类型List< SelectListItem>所以当ViewBag在响应中呈现视图时它不会被绑定。



@ Html.DropDownList（PropertyName，selectList）的问题是我是为它分配与为其获取数据的属性相同的名称。将Name字符串更改为PropertyNameSelect之后，所选值正确呈现为http响应字符串。

Figured out my problems. Turns out is was something very simple. The problem was with the view bag.

Problem with @Html.DropDownListFor(Model => Model.Property, selectList) is that the Model.Property was not of the type List<SelectListItem> so it wouldn't be bound when the ViewBag rendered the view in the response.

Problem with @Html.DropDownList("PropertyName", selectList) is that I was assigning it the same name as the property it was fetching data for. Once I changed the Name string to something like "PropertyNameSelect," the selected values rendered correctly to the http response string.

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