MVC 应用程序中的 OptimisticConcurrencyException

Question

我正在关注 MvcMusicStore 教程，突然间我遇到了编辑功能的问题，这在我编写该部分代码时肯定没有发生。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 Edit 视图发布提交编辑时，ModelState.Valid 表达式通过，但是传递的专辑参数的 AlbumId 始终为零，尽管在编辑方法的 GET 部分专辑 ID 在那里。所以我想知道这是否是 db.Entry(album) 表达式不断返回 0 行的原因？无论如何，这就是发生的事情，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.

这种情况以前没有发生过，自从发生这种情况后，我从教程下载中复制并粘贴了这个控制器和相应的编辑视图。同样的错误。这是编辑视图，但现在我想知道问题是否完全不在其他地方，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

接受的答案here 应该会有所帮助。最直接的解决方法是将 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;