MVC应用程序中的OptimisticConcurrencyException

Question

I'm following the MvcMusicStore tutorial, and all of a sudden I'm having a problem with the editing functionality, which definitely was not going on when I coded that portion. Here's the relevant controller...

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);
        }
    }
}

When the Edit view posts to submit an edit, the ModelState.Valid expression passes, but the AlbumId of the passed album parameter is always zero, though on the GET portion on of the edit methods the AlbumId is there. So I'm wondering if maybe this is the reason the db.Entry(album) expression keeps returning 0 rows? Anyway, that's what's happening, the db.Entry() function keeps returning 0 rows, and then when the context tries to save it throws 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.

This wasn't happening before, and since this happened I've literally copied and pasted this controller and the corresponding edit view from the tutorial download. Same error. Here's the edit view, but now I'm wondering if maybe the issue isn't somewhere else entirely, though I can't imagine where.

@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

The accepted answer here should help out. The most straight forward way around this is to add the id parameter to the Edit() Post method, and then update the Album object, ie

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