MVC应用程序中的OptimisticConcurrencyException

Question

我正在关注MvcMusicStore教程，突然之间我在编辑功能方面遇到了问题，当我对该部分进行编码时，这肯定没有发生。 这是相关的控制器...

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Entity;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using MvcMusicStore.Models;

namespace MvcMusicStore.Controllers
{
    public class StoreManagerController : Controller
    {
        private MusicStoreEntities db = new MusicStoreEntities();

        //
        // GET: /StoreManager/

        public ViewResult Index()
        {
            var albums = db.Albums.Include(a => a.Genre).Include(a => a.Artist);
            return View(albums.ToList());
        }

        //
        // GET: /StoreManager/Details/5

        public ViewResult Details(int id)
        {
            Album album = db.Albums.Find(id);
            return View(album);
        }

        //
        // GET: /StoreManager/Create

        public ActionResult Create()
        {
            ViewBag.GenreId = new SelectList(db.Genres, "GenreId", "Name");
            ViewBag.ArtistId = new SelectList(db.Artists, "ArtistId", "Name");
            return View();
        }

        //
        // POST: /StoreManager/Create

        [HttpPost]
        public ActionResult Create(Album album)
        {
            if (ModelState.IsValid)
            {
                db.Albums.Add(album);
                db.SaveChanges();
                return RedirectToAction("Index");
            }

            ViewBag.GenreId = new SelectList(db.Genres, "GenreId", "Name", album.GenreId);
            ViewBag.ArtistId = new SelectList(db.Artists, "ArtistId", "Name", album.ArtistId);
            return View(album);
        }

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

        public ActionResult Edit(int id)
        {
            Album album = db.Albums.Find(id);
            ViewBag.GenreId = new SelectList(db.Genres, "GenreId", "Name", album.GenreId);
            ViewBag.ArtistId = new SelectList(db.Artists, "ArtistId", "Name", album.ArtistId);
            return View(album);
        }

        //
        // POST: /StoreManager/Edit/5

        [HttpPost]
        public ActionResult Edit(Album album)
        {
            if (ModelState.IsValid)
            {
                db.Entry(album).State = EntityState.Modified;
                db.SaveChanges();
                return RedirectToAction("Index");
            }
            ViewBag.GenreId = new SelectList(db.Genres, "GenreId", "Name", album.GenreId);
            ViewBag.ArtistId = new SelectList(db.Artists, "ArtistId", "Name", album.ArtistId);
            return View(album);
        }

        //
        // GET: /StoreManager/Delete/5

        public ActionResult Delete(int id)
        {
            Album album = db.Albums.Find(id);
            return View(album);
        }

        //
        // POST: /StoreManager/Delete/5

        [HttpPost, ActionName("Delete")]
        public ActionResult DeleteConfirmed(int id)
        {
            Album album = db.Albums.Find(id);
            db.Albums.Remove(album);
            db.SaveChanges();
            return RedirectToAction("Index");
        }

        protected override void Dispose(bool disposing)
        {
            db.Dispose();
            base.Dispose(disposing);
        }
    }
}

当“编辑”视图发布以提交编辑时，将传递ModelState.Valid表达式， 但是传递的专辑参数的AlbumId始终为零，尽管在编辑方法的GET部分上，该AlbumId也存在。 所以我想知道这是否是db.Entry（album）表达式始终返回0行的原因吗？ 无论如何，这就是正在发生的事情，db.Entry（）函数不断返回0行，然后当上下文尝试保存它时抛出Exception Details: System.Data.OptimisticConcurrencyException: Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries. Exception Details: System.Data.OptimisticConcurrencyException: Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries.

以前从未发生过这种情况，并且由于发生了这种情况，因此我从字面上直接复制并粘贴了该控制器和教程下载中的相应编辑视图。 同样的错误。 这是编辑视图，但是现在我想知道问题是否还不完全在其他地方，尽管我无法想象在哪里。

@model MvcMusicStore.Models.Album

@{
    ViewBag.Title = "Edit";
}

<h2>Edit</h2>

<script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script>

@using (Html.BeginForm()) {
    @Html.ValidationSummary(true)
    <fieldset>
        <legend>Album</legend>

        @Html.HiddenFor(model => model.AlbumId)

        <div class="editor-label">
            @Html.LabelFor(model => model.GenreId, "Genre")
        </div>
        <div class="editor-field">
            @Html.DropDownList("GenreId", String.Empty)
            @Html.ValidationMessageFor(model => model.GenreId)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.ArtistId, "Artist")
        </div>
        <div class="editor-field">
            @Html.DropDownList("ArtistId", String.Empty)
            @Html.ValidationMessageFor(model => model.ArtistId)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.Title)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Title)
            @Html.ValidationMessageFor(model => model.Title)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.Price)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Price)
            @Html.ValidationMessageFor(model => model.Price)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.AlbumArtUrl)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.AlbumArtUrl)
            @Html.ValidationMessageFor(model => model.AlbumArtUrl)
        </div>

        <p>
            <input type="submit" value="Save" />
        </p>
    </fieldset>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

Answer 1

此处接受的答案应该会有所帮助。 解决此问题的最直接的方法是将id参数添加到Edit（）Post方法，然后更新Album对象，即

[HttpPost]
public ActionResult Edit(Album album, int id)
{
    if (ModelState.IsValid)
    {
        album.AlbumId = id;
        db.Entry(album).State = EntityState.Modified;