选择MVC5剃刀html.dropdownlistfor设定值时，在数组 [英] MVC5 Razor html.dropdownlistfor set selected when value is in array

问题描述

我开发一个ASP.NET MVC应用5，用C＃和.NET Framework 4.6.1。

I'm developing an ASP.NET MVC 5 application, with C# and .NET Framework 4.6.1.

我有这样的查看：

@model MyProject.Web.API.Models.AggregationLevelConfViewModel

[...]

@Html.DropDownListFor(m => m.Configurations[0].HelperCodeType, (SelectList)Model.HelperCodeTypeItems, new { id = "Configurations[0].HelperCodeType" })

的视图模型是：

public class AggregationLevelConfViewModel
{
    private readonly List<GenericIdNameType> codeTypes;
    private readonly List<GenericIdNameType> helperCodeTypes;

    public IEnumerable<SelectListItem> CodeTypeItems
    {
        get { return new SelectList(codeTypes, "Id", "Name"); }
    }

    public IEnumerable<SelectListItem> HelperCodeTypeItems
    {
        get { return new SelectList(helperCodeTypes, "Id", "Name"); }
    }

    public int ProductionOrderId { get; set; }

    public string ProductionOrderName { get; set; }

    public IList<Models.AggregationLevelConfiguration> Configurations { get; set; }

    public AggregationLevelConfViewModel()
    {
        // Load CodeTypes to show it as a DropDownList
        byte[] values = (byte[])Enum.GetValues(typeof(CodeTypes));

        codeTypes = new List<GenericIdNameType>();
        helperCodeTypes = new List<GenericIdNameType>();

        for (int i = 0; i < values.Length; i++)
        {
            GenericIdNameType cType = new GenericIdNameType()
            {
                Id = values[i].ToString(),
                Name = EnumHelper.GetDescription((CodeTypes)values[i])
            };

            if (((CodeTypes)values[i]) != CodeTypes.NotUsed)
                codeTypes.Add(cType);

            helperCodeTypes.Add(cType);
        }
    }
}

和 Models.AggregationLevelConfiguration 是：

public class AggregationLevelConfiguration
{
    public byte AggregationLevelConfigurationId { get; set; }
    public int ProductionOrderId { get; set; }
    public string Name { get; set; }
    public byte CodeType { get; set; }
    public byte HelperCodeType { get; set; }
    public int PkgRatio { get; set; }
    public int RemainingCodes { get; set; }
}

我需要这些属性来设置选择的值：

I need to set selected value in these properties:

public IEnumerable<SelectListItem> CodeTypeItems
{
    get { return new SelectList(codeTypes, "Id", "Name"); }
}

public IEnumerable<SelectListItem> HelperCodeTypeItems
{
    get { return new SelectList(helperCodeTypes, "Id", "Name"); }
}

但我不能将其设置在新的SelectList（codetypes的，ID，姓名）; 或新的SelectList （辅助codetypes的，ID，姓名）; ，因为选择的值是配置数组：田 AggregationLevelConfiguration。codeTYPE 和 AggregationLevelConfiguration.Helper codeTYPE 。

But I can't set it in new SelectList(codeTypes, "Id", "Name"); or new SelectList(helperCodeTypes, "Id", "Name"); because the selected value are in Configurations array: fields AggregationLevelConfiguration.CodeType and AggregationLevelConfiguration.HelperCodeType.

我觉得我有在视图中选择设定值，但我不知道该怎么办了。

I think I have to set selected value in the View, but I don't know how to do it.

我怎么可以设置选择的值？

How can I set the selected values?

推荐答案

不幸的是 @ Html.DropDownListFor（）在一个循环中呈现控件时的表现有点不同于其他佣工。这一直是pviously报告为C $ CPLEX在$一个问题$ P $（不知道它的一个bug或只是一个限制）

Unfortunately @Html.DropDownListFor() behaves a little differently than other helpers when rendering controls in a loop. This has been previously reported as an issue on CodePlex (not sure if its a bug or just a limitation)

该是解决此，以确保正确的选项2选项是基于模型属性选择了

The are 2 option to solve this to ensure the correct option is selected based on the model property

选项1 （使用 EditorTemplate ）

创建自定义的 EditorTemplate 为集合中的类型。在 /Views/Shared/EditorTemplates/AggregationLevelConfiguration.cshtml 创建一个部分（注意名称必须与类的名称相匹配

Create a custom EditorTemplate for the type in the collection. Create a partial in /Views/Shared/EditorTemplates/AggregationLevelConfiguration.cshtml (note the name must match the name of the type

@model yourAssembly.AggregationLevelConfiguration
@Html.DropDownListFor(m => m.HelperCodeType, (SelectList)ViewData["CodeTypeItems"])
.... // other properties of AggregationLevelConfiguration

，然后在主视图，通过的SelectList 到 EditorTemplate 为 additionalViewData

@using (Html.BeginForm())
{
  ...
  @Html.EditorFor(m => m.Configurations , new { CodeTypeItems = Model.CodeTypeItems })
  ...

选项2 （生成一个新的的SelectList 在每次迭代中，并设置了selectedValue ）

Option 2 (generate a new SelectList in each iteration and set the selectedValue)

在这个选项你的财产 codeTypeItems 应该是的IEnumerable＆LT; GenericIdNameType＆GT; ，而不是的SelectList （或者只是让 codetypes的的公共属性）。然后在主视图

In this option your property CodeTypeItems should to be IEnumerable<GenericIdNameType>, not a SelectList (or just make codeTypes a public property). Then in the main view

@Html.DropDownListFor(m => m.Configurations[0].HelperCodeType, new SelectList(Model.CodeTypeItems, "Id", "Name", Model.Configurations[0].HelperCodeType)

边注：没有必要使用新{ID =配置[0] .Helper codeTYPE - 在 DropDownListFor （）方法已经产生了 ID 属性

Side note: there is no need to use new { id = "Configurations[0].HelperCodeType" - the DropDownListFor() method already generated that id attribute

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