MVC列表强类型查看DropDownListFor不显示当前值 [英] Mvc List Strongly type View DropDownListFor not showing current value

问题描述

我有以下 dropdownlistfor 控制

@Html.DropDownListFor(m => item.RelationShipId, new SelectList(ViewBag.RelationShip,"Id", "Title"), new { @id = "ddl_" + @item.UserID, @class = "form-control", onchange = "update(this,'" + @item.UserID + "','" + @item.SentByUserId + "');" })

我这个绑定强类型视图这样的 @model名单＆LT; MvcUI.Models.UserDetails＆GT;

在 ViewBag.RelationShip 我下面的列表

public static List<IDTitleDTO> DataTableToRelationshipList(this DataTable table)
{
        var list = table.AsEnumerable()
            .Select(dr =>
                new IDTitleDTO
                {
                    Id = dr.Field<int>("RelationShipId"),
                    Title = dr.Field<string>("RelationShipName")
                }).ToList();
        return list;
}

我传递的List 的UserDetails 模型对我的看法。这里是我的的UserDetails 模式

I am passing List Of UserDetails model to my view. Here is my UserDetails Model

public class UserFriendDetails
{
    public string UserID { get; set; }
    public string UserName { get; set; }
    public string Firstname { get; set; }
    public int? RelationShipId { get; set; }
    ....
    ...
    Other fields
}

在列表假设我有3个纪录。从他们的2条RelationShipId为空。如果是null，则我设置-1是 - 选择 - 在剩下的一个记录我有RelationShipId想我有13.视图中打开它绑定 - 选择 - 对于前两个记录。但对于第三个记录是没有约束力的ViewBag适当的值。哪里是问题，我无法弄清楚。有些人可以帮我解决这个？

Suppose in a list I have 3 record. Out of them 2 records RelationShipId is null. If it's null then I am setting -1 which is -- Select --. In remaining one record I have RelationShipId suppose I have 13. When view opens It is binding -- Select -- for first two record. But for 3rd record it is not binding appropriate value from ViewBag. I can't figure it out where is the issue. Can some one help me to solve this?

在这里，我创建了一个简单的动作即用户

Here I have created one simple action i.e. user

[AllowAnonymous]
public ActionResult User()
{
    var model = new List<UserDetails>();
    model.Add(new UserDetails { Id = 1, Fname = "ajay", RelationId = 3});
    model.Add(new UserDetails { Id = 2, Fname = "vijay", RelationId = 1 });
    model.Add(new UserDetails { Id = 3, Fname = "John", RelationId = 2 });

    var rList = new List<IdTitleDTO>();
    rList.Add(new IdTitleDTO { Id = 1 , Title = "M"});
    rList.Add(new IdTitleDTO { Id = 2, Title = "F" });
    rList.Add(new IdTitleDTO { Id = 3, Title = "B" });

    ViewBag.Rel = rList;
    return View(model);
}

下面是我的 user.cshtml

@model List<WebApplicationDropDown.Models.UserDetails>
<table class="table">
    <tr>
        <th>
            Fname
        </th>
        <th></th>
    </tr>

    @*@foreach (var item in Model) {*@
    @for (int i = 0; i < Model.Count(); i++)
    {
        <tr>
            <td>
                @Html.DisplayFor(modelItem => Model[i].Fname)
            </td>
            <td>
                @Html.DropDownListFor(modelItem => Model[i].RelationId, new SelectList(ViewBag.Rel, "Id", "Title"), "--Select--")
            </td>
        </tr>
    }
</table>

在此查看它没有约束力relationId。默认情况下它显示 - 选择 - ，而不是呈现如下关系

In this View it is not binding relationId. By default it is showing -- Select -- instead of showing following relation

ajay - B
Vijay - M
John - F

请参阅下图

编辑模板的UserDetails。 CSHTML

Editor template UserDetails.cshtml

@model WebApplicationDropDown.Models.UserDetails


@Html.DropDownListFor(m => m.RelationId, (SelectList)ViewData["RelationShipList"])

View.cshtml

@model IEnumerable<WebApplicationDropDown.Models.UserDetails>
<table class="table">
    <tr>
        <th>
            Fname
        </th>
        <th></th>
    </tr>

    @foreach (var item in Model)
    {
        <tr>
            <td>
                @Html.DisplayFor(modelItem => item.Fname)
            </td>
            <td>
                @*@Html.DropDownListFor(modelItem => item.RelationId, new SelectList(ViewBag.Rel, "Id", "Title"), "--Select--")*@
                @Html.EditorFor(m => m, new { RelationShipList = new SelectList(ViewBag.Rel, "Id", "Title") })
            </td>
        </tr>
    }
</table>

请参见下面的截图

推荐答案

创建自定义的 EditorTemplate 类型的 UserFriendDetails

在 /Views/Shared/EditorTemplates/UserFriendDetails.cshtml

@model UserFriendDetails
@Html.TextBoxFor(m => m.UserName)
....
@Html.DropDownLstFor(m => m.RelationShipId, (SelectList)ViewData["RelationShipList"])

然后在主视图，通过的SelectList 使用附加视图数据模板

@model IEnumerable<UserFriendDetails>
....
@Html.EditorFor(m => m, new { RelationShipList = new SelectList(ViewBag.RelationShip,"Id", "Title") })

这将产生正确的名称属性绑定到你的收集，例如：

This will generate the correct name attributes to bind to you collection, for example

<select name="[0].RelationShipId" ..>
<select name="[1].RelationShipId" ..>

和选择的基础上每 RelationShipId 属性的值正确的选项。

and select the correct option based on the value of each RelationShipId property.

附注：我建议你删除新{@id =ddl_+ @ item.UserID，... 并使用默认的 ID 由助手生成的。它不清楚是什么的onchange 属性做什么，但我也建议你使用的非侵入式JavaScript 而不是行为污染您的标记。

Side note: I suggest you remove the new { @id = "ddl_" + @item.UserID,... and use the default id generated by the helper. Its not clear what the onchange attribute is doing but I also suggest you use unobtrusive javascript rather than polluting your markup with behavior.

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