c# - System.Data.Entity.Infrastructure.DbUpdateConcurrencyException。存储更新、插入或删除语句影响了意外的行数 (0)

Question

模型这些是模型类，我正在使用 Entity Framework 。我正在使用这些模型来实现级联下拉列表。

  public class League
    {
        public int Id { get; set; }
        public string League1 { get; set; }
        public string Icon { get; set; }

        public virtual ICollection<LeagueDivision> LeagueDivisions { get; set; }
    }

  public class LeagueDivision
    {
        public int Id { get; set; }
        public Nullable<int> LeagueId { get; set; }
        public string Name { get; set; }
        public string Icon { get; set; }

        public virtual League League { get; set; }
    }  

  public partial class CalculatorPrice
    {
        public int Id { get; set; }
        public int LeagueId { get; set; }
        public int LeagueDivisionId { get; set; }
        public Nullable<decimal> Price { get; set; }
    } 

 public class ViewModelForHostBooster
    {
        [Required(ErrorMessage = "Please enter price")]
        [Display(Name = "Price")]
        public decimal Price { get; set; }       

        [Required(ErrorMessage = "Please select a league")]
        [Display(Name = "League")]

        public int? SelectedLeague { get; set; }
        [Required(ErrorMessage = "Please select a league division")]
        [Display(Name = "League Division")]

        public int? SelectedLeagueDivision { get; set; }

        public SelectList LeagueList { get; set; }
        public SelectList LeagueDivisionList { get; set; }    

    }

Controller / Action 在 HttpGet 中，我刚刚填充了级联下拉列表并且工作正常，现在我正在为此实现 Httppost。我想根据从下拉列表中选择的列表项存储 price，如果 price 已经存在，那么我想更新它。第一次我可以成功添加 price 但是第二次当我尝试更新它时我得到 System.Data.Entity.Infrastructure.DbUpdateConcurrencyException 请任何人指导我如何处理这个。

[HttpPost]
 public ActionResult IndexDropDown(ViewModelForHostBooster model)
    {
        if (!ModelState.IsValid)
        {
            ConfigureViewModel(model);
            return View(model);
        }
        else
        {
            HostBoostersDBEntities2 db = new HostBoostersDBEntities2();
            CalculatorPrice calculatePrice = new CalculatorPrice();
             var  calculatePriceExistsOrNot =  db.CalculatorPrices
                .Where(x => x.LeagueId == model.SelectedLeague
                    &&
                    x.LeagueDivisionId == model.SelectedLeagueDivision).ToList();
             if (calculatePriceExistsOrNot.Count > 0)
            {

                calculatePrice.LeagueId = (int)model.SelectedLeague;
                calculatePrice.LeagueDivisionId = (int)model.SelectedLeagueDivision;
                calculatePrice.Price = model.Price;
                db.Entry(calculatePrice).State = EntityState.Modified;

Exception occurs here in line db.SaveChanges(); 'System.Data.Entity.Infrastructure.DbUpdateConcurrencyException' occurred in EntityFramework.dll but was not handled in user code. Additional information: 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.

                db.SaveChanges();
            }
            else
            {
                calculatePrice.LeagueId = (int)model.SelectedLeague;
                calculatePrice.LeagueDivisionId = (int)model.SelectedLeagueDivision;
                calculatePrice.Price = model.Price;
                db.CalculatorPrices.Add(calculatePrice);
                db.SaveChanges();
            }


        }
        ConfigureViewModel(model);
        return View(model);
    }

查看

  @using (Html.BeginForm("IndexDropDown", "DropDown", FormMethod.Post,
                                      new { enctype = "multipart/form-data" }))
{
    <div>
        @Html.LabelFor(m => m.Price, new { @class ="control-lebel"})
        @Html.TextBoxFor(m => m.Price, new { @class = "form-control"})
        @Html.ValidationMessageFor(m => m.Price)
    </div>

    <div>
        @Html.LabelFor(m => m.SelectedLeague ,new { @class ="control-lebel"})
        @Html.DropDownListFor(m => m.SelectedLeague, Model.LeagueList, new { @class = "form-control"})
        @Html.ValidationMessageFor(m => m.SelectedLeague)
    </div>
    <div>
        @Html.LabelFor(m => m.SelectedLeagueDivision ,new { @class ="control-lebel"})
        @Html.DropDownListFor(m => m.SelectedLeagueDivision, Model.LeagueDivisionList, new { @class = "form-control" })
        @Html.ValidationMessageFor(m => m.SelectedLeagueDivision)
    </div>
    <input type="submit" value="save" />
}

Answer 1

[HttpPost]
 public ActionResult IndexDropDown(ViewModelForHostBooster model)
    {
        if (!ModelState.IsValid)
        {
            ConfigureViewModel(model);
            return View(model);
        }
        else
        {
            HostBoostersDBEntities2 db = new HostBoostersDBEntities2();
            CalculatorPrice calculatePrice  =  db.CalculatorPrices
                .Where(x => x.LeagueId == model.SelectedLeague
                    &&
                    x.LeagueDivisionId == model.SelectedLeagueDivision).FirstOrDefault();
             if (calculatePrice != null)
            {
                calculatePrice.LeagueId = (int)model.SelectedLeague;
                calculatePrice.LeagueDivisionId = (int)model.SelectedLeagueDivision;
                calculatePrice.Price = model.Price;
                //db.Entry(calculatePrice).State = EntityState.Modified;
                db.SaveChanges();
            }
            else
            {
                calculatePrice = new CalculatorPrice();
                calculatePrice.LeagueId = (int)model.SelectedLeague;
                calculatePrice.LeagueDivisionId = (int)model.SelectedLeagueDivision;
                calculatePrice.Price = model.Price;
                db.CalculatorPrices.Add(calculatePrice);
                db.SaveChanges();
            }


        }
        ConfigureViewModel(model);
        return View(model);
    }