当我将 [Required] 添加到类时出现异常错误答案

【问题标题】：exception error when I add [Required] to class当我将 [Required] 添加到类时出现异常错误
【发布时间】：2015-01-02 13:39:27
【问题描述】：

将[Required] 添加到类时出现异常：

EntityFramework.dll 中出现“System.InvalidOperationException”类型的异常，但未在用户代码中处理。

附加信息：支持“MovieDBContext”上下文的模型自数据库创建以来已更改。考虑使用 Code First 迁移来更新数据库。”

班级

public class Movie
{
    public int ID { get; set; }

    [StringLength(60, MinimumLength = 3)]
    [Required]
    public string Title { get; set; }

    [Display(Name = "Release Date"), DataType(DataType.Date)]
    [Range(typeof(DateTime), "1/1/1966", "1/1/2020")]
    public DateTime ReleaseDate { get; set; }

    [Required]
    [StringLength(30)]
    public string Genre { get; set; }

    [Range(1, 100),DataType(DataType.Currency)]
    public decimal Price { get; set; }

    [StringLength(5)]
    public string Rating { get; set; }
}

public class MovieDBContext : DbContext
{
    public DbSet<Movie> Movies { get; set; }
}

控制器

namespace ICmovie.Controllers
{
    public class MoviesController : Controller
    {
        private MovieDBContext db = new MovieDBContext();

        // GET: Movies
        public ActionResult Index(string movieGenre, string searchString)
        {
            var GenreLst = new List<string>();

            var GenreQry = from d in db.Movies
                           orderby d.Genre
                           select d.Genre;

            GenreLst.AddRange(GenreQry.Distinct());
            ViewBag.movieGenre = new SelectList(GenreLst);

            var movies = from m in db.Movies
                         select m;

            if (!String.IsNullOrEmpty(searchString))
            {
                movies = movies.Where(s => s.Title.Contains(searchString));
            }

            if (!string.IsNullOrEmpty(movieGenre))
            {
                movies = movies.Where(x => x.Genre == movieGenre);
            }

            return View(movies);
        }

        // GET: Movies/Details/5
        public ActionResult Details(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }

            Movie movie = db.Movies.Find(id);

            if (movie == null)
            {
                return HttpNotFound();
            }

            return View(movie);
        }

        // GET: Movies/Create
        public ActionResult Create()
        {
            return View();
        }

        // POST: Movies/Create
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
        // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Create([Bind(Include = "ID,Title,ReleaseDate,Genre,Price,Rating")] Movie movie)
        {
            if (ModelState.IsValid)
            {
                db.Movies.Add(movie);
                db.SaveChanges();
                return RedirectToAction("Index");
            }

            return View(movie);
        }

        // GET: Movies/Edit/5
        public ActionResult Edit(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }

            Movie movie = db.Movies.Find(id);

            if (movie == null)
            {
                return HttpNotFound();
            }

            return View(movie);
        }

        // POST: Movies/Edit/5
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
        // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Edit([Bind(Include = "ID,Title,ReleaseDate,Genre,Price,Rating")] Movie movie)
        {
            if (ModelState.IsValid)
            {
                db.Entry(movie).State = EntityState.Modified;
                db.SaveChanges();
                return RedirectToAction("Index");
            }

            return View(movie);
        }

        // GET: Movies/Delete/5
        public ActionResult Delete(FormCollection fcNotUsed, int id = 0)
        {
            Movie movie = db.Movies.Find(id);

            if (movie == null)
            {
                return HttpNotFound();
            }

            db.Movies.Remove(movie);
            db.SaveChanges();

            return RedirectToAction("Index");
        }

        // POST: Movies/Delete/5
        [HttpPost, ActionName("Delete")]
        [ValidateAntiForgeryToken]
        public ActionResult DeleteConfirmed(int id)
        {
            Movie movie = db.Movies.Find(id);
            db.Movies.Remove(movie);
            db.SaveChanges();
            return RedirectToAction("Index");
        }

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

【问题讨论】：

您在哪个属性中添加了[Required] ??错误发生在控制器的哪个方法中？？
您是否尝试从数据库中刷新您的模型？
方法控制器错误是“var GenreQry = from d in db.Movies orderby d.Genre select d.Genre;”
如果您删除Required 属性，那么一切正常吗？或者您仍然遇到同样的问题？
再次 - which [Required] 属性你在说什么？？？有两个 - 一个在Title，一个在Genre .....

标签： c# asp.net-mvc entity-framework

【解决方案1】：

将 [Required] 添加到 int、DateTime 或 Decimal 等字段实际上可以将数据库中的 Nullable 属性更改为 false，因此被视为模型更改。您可能必须运行 Add-Migration 来创建迁移以更新数据库以反映此更改。

【讨论】：