在ASP.NET MVC中使用MultiSelectList

Question

我正在嘗試為book創建編輯表單（ID為1），我希望選擇列表選擇從數據庫中檢索的現有作者。 id為1的書具有id為1的作者，但HTML不顯示該書的id為1的選定作者。

我覺得ViewData [“SelectedAuthors”]參數在Book.ascx源文件的MultiSelectList函數中作為IEnumerable有問題

另一個問題是，如何使用MultiSelectList將“first_name”和“last_name”結合起來進行文本顯示？ 我只能選擇“first_name”

StoreManagerViewModel.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using BookStore.Models;

namespace BookStore.ViewModels
{
    public class StoreManagerViewModel
    {
        public book Book { get; set; }
        public List<author> Authors { get; set; }
        public List<category> Categories { get; set; }
        public List<int> SelectedAuthors { get; set; }
    }
}

StoreManagerController.cs

using System;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using BookStore.Models;
using BookStore.ViewModels;

namespace BookStore.Controllers
{
    public class StoreManagerController : Controller
    {
        BookStoreEntities storeDB = new BookStoreEntities();

        //
        // GET: /StoreManager/Edit/5

        public ActionResult Edit(int id)
        {
            var viewModel = new StoreManagerViewModel
            {
                Book = storeDB.books.Single(a => a.book_id == id),
                Categories = storeDB.categories.ToList(),
                Authors = storeDB.authors.ToList(),
                SelectedAuthors = (from a in storeDB.books.Single(b => b.book_id == id).authors
                                    select a.author_id
                                  ).ToList()
            };

            //I have debug and have seen that the SelectedAuthors list has one author_id as 1

            return View(viewModel);
        }

    }
}

Store.ascx（部分視圖）用於StoreManagerController的'edit'方法

<%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<BookStore.Models.book>" %>

    <% using (Html.BeginForm()) {%>
        <%: Html.ValidationSummary(true) %>


            <div class="editor-label">
                <%: Html.LabelFor(model => model.authors) %>
            </div>
            <div class="editor-field">
                <%: Html.ListBox("author_id", new MultiSelectList(ViewData["authors"] as IEnumerable, "author_id", "first_name", ViewData["SelectedAuthors"] as IEnumerable))%>
            </div>

    <% } %>

Book.ascx局部視圖的HTML結果

<select id="Book_author_id" multiple="multiple" name="Book.author_id">
<option value="1">Bikkhu</option>
<option value="2">Buddha</option>
<option value="3">William</option>
<option value="4">Anthony</option>
</select>

Answer 1

您正在使用需要綁定到作為集合的模型屬性的多選列表。 在您的情況下，您綁定到"author_id" ，它只能包含一個選定的項目ID。 您也在部分使用ViewData["authors"]和ViewData["SelectedAuthors"] ，但在控制器操作中，不清楚這些屬性是如何填充的。

Answer 2

它現在已經解決了，我沒有在“edit.aspx”視圖中將“SelectedAuthors”提供給“Book.ascx”的局部視圖

<%: Html.EditorFor(model => model.Book,
    new { Authors = Model.Authors, Categories = Model.Categories, SelectedAuthors = Model.SelectedAuthors }) %>