System.Data.Entity.Infrastructure.DbUpdateConcurrentExceptio

模型这些是模型类，我使用的是实体框架。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; }    
    }

控制器/操作在HttpGet中，我刚刚填充了级联下拉列表，现在工作正常，我正在为此实现Httppost。我想存储价格，具体取决于从下拉列表中选择的列表项，如果定价已经存在，则我想更新它。第一次我可以成功添加价格，但第二次当我尝试更新它时，我得到了System.Data.Entity.Infrastructure.DbUpdateConcurrentException请任何人指导我如何处理此问题。

[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;

这里的db行出现异常。SaveChanges((EntityFramework.dll中出现"System.Data.Entity.Infrastructure.DbUpdateConcurrentException"，但未在用户代码中处理。其他信息：存储更新、插入或删除语句影响了意外的行数(0(。自加载实体以来，实体可能已被修改或删除。刷新ObjectStateManager条目。

                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" />
}