如何解决实体框架 - 如何在没有表单的情况下添加数据库条目
通常我会使用“创建”表单添加新的数据库条目，就像您得到的模板一样：
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create([Bind(Include = "MyObjectProperties")] MyObject MyObjectName)
{
if (ModelState.IsValid)
{
db.MyObjects.Add(MyObjectName);
db.SaveChanges();
return RedirectToAction("Index");
}
return View(MyObjectName);
}
哪个工作得很好。但是，我试图删除数据库中的所有条目，然后再一一添加。目的是在表格中填充一年中每周的截止日期，此方法将重置截止日期并为给定年份设置正确的日期。这是执行该任务的方法：
public bool ResetDeadlines()
{
//db.Canteen_Deadlines.RemoveRange(db.Canteen_Deadlines);
int monthOfLastWeek = 1;
DateTime deadlineDate;
int weekOfMonth = 0;
int year = DateTime.Now.Year;
for (var i = 1; i < 53; i++)
{
if (i == 1)
year += 1;
else
year = DateTime.Now.Year;
deadlineDate = GetThursdayOfWeek(year,i).AddDays(-7); //Gets the thursday of the week before,because that is the deadline for that week.
weekOfMonth = monthOfLastWeek < deadlineDate.Month ? 1 : weekOfMonth + 1;
var newDeadline = new Canteen_Deadlines
{
N = DaysFromNewYear(year,deadlineDate),DeadlineDate = deadlineDate,WeekNo = (byte)i,MonthNo = (byte)deadlineDate.Month,QuarterNo = (byte)GetQuarterNumber(deadlineDate.Month),YearNo = (short)year,DayofWeek = 4,LastDowInMonth = IsLastDoWInMonth(deadlineDate),DoWAsc = (byte)weekOfMonth
};
db.Canteen_Deadlines.Add(newDeadline);
//db.Entry(newDeadline).State = EntityState.Added;
db.SaveChanges();
monthOfLastWeek = deadlineDate.Month;
}
return true;
}
当我执行 db.SaveChanges(); 时出现问题。它会给我一个 dbupdateConcurrencyException，表示数据库中的任何行都没有受到影响。我似乎无法弄清楚我的方法和模板 create 方法之间的区别。其他在线帖子更关注使用模板创建方法时出现的这个问题，而人们没有在他们的 ID 上使用“Html.HiddenFor”。这对我来说不是一个可行的解决方案，因为我没有使用表单，因此无法使用 Html 助手。用户只需按下“重置截止日期”按钮即可。
对象上的“N”属性是它们的键。它是给定日期在一年中的天数，这意味着 1 月 16 日将是 N = 16。由于截止日期仅为 1 年，因此 N 值不会冲突，因此应该能够用作键。
如何将这些条目成功保存到数据库中？我已经注释掉了 db.remove 方法，只是为了让添加的条目起作用。我也尝试将入口状态设置为添加，但这也不起作用。我尝试调试并确认对象的所有属性都已正确初始化。
完全例外：
[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. See http://go.microsoft.com/fwlink/?LinkId=472540 for information on understanding and handling optimistic concurrency exceptions.]
System.Data.Entity.Core.Mapping.Update.Internal.UpdateTranslator.ValidateRowsAffected(Int64 rowsAffected,UpdateCommand source) +142
System.Data.Entity.Core.Mapping.Update.Internal.UpdateTranslator.Update() +525
System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction(Func`1 func,IDbExecutionStrategy executionStrategy,Boolean startLocalTransaction,Boolean releaseConnectionOnSuccess) +453
System.Data.Entity.Core.Objects.ObjectContext.SaveChangesToStore(SaveOptions options,Boolean startLocalTransaction) +252
System.Data.Entity.sqlServer.DefaultsqlExecutionStrategy.Execute(Func`1 operation) +206
System.Data.Entity.Core.Objects.ObjectContext.SaveChangesInternal(SaveOptions options,Boolean executeInExistingTransaction) +270
System.Data.Entity.Internal.InternalContext.SaveChanges() +145
[dbupdateConcurrencyException: Store update,or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. See http://go.microsoft.com/fwlink/?LinkId=472540 for information on understanding and handling optimistic concurrency exceptions.]
System.Data.Entity.Internal.InternalContext.SaveChanges() +280
MyProject.Models.Services.DeadlinesService.ResetDeadlines() in \\PROJECTPATH\Models\Services\DeadlinesService.cs:49
MyProject.Controllers.AdminController.ResetDeadlines() in \\PROJECTPATH\Controllers\AdminController.cs:254
lambda_method(Closure,ControllerBase,Object[] ) +87
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext,ActionDescriptor actionDescriptor,IDictionary`2 parameters) +35
System.Web.Mvc.Async.<>c.<BeginInvokeSynchronousActionMethod>b__9_0(IAsyncResult asyncResult,ActionInvocation innerInvokeState) +39
System.Web.Mvc.Async.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult) +77
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) +42
System.Web.Mvc.Async.<>c__displayClass11_0.<InvokeActionMethodFilterasynchronouslyRecursive>b__0() +80
System.Web.Mvc.Async.<>c__displayClass11_2.<InvokeActionMethodFilterasynchronouslyRecursive>b__2() +387
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) +42
System.Web.Mvc.Async.<>c__displayClass3_6.<BeginInvokeAction>b__4() +50
System.Web.Mvc.Async.<>c__displayClass3_1.<BeginInvokeAction>b__1(IAsyncResult asyncResult) +188
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +38
System.Web.Mvc.<>c.<BeginExecuteCore>b__152_1(IAsyncResult asyncResult,ExecuteCoreState innerState) +26
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +73
System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +52
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +39
System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +38
System.Web.Mvc.<>c.<BeginProcessRequest>b__20_1(IAsyncResult asyncResult,ProcessRequestState innerState) +40
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +73
System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +38
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +602
System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) +195
System.Web.HttpApplication.ExecuteStep(IExecutionStep step,Boolean& completedSynchronously) +128
编辑： 控制器动作：
public ActionResult ResetDeadlines()
{
deadlinesService.ResetDeadlines();
return RedirectToAction("IndexDeadlines");
}
查看：
@using (Html.BeginForm())
{
@Html.AntiForgeryToken()
<div class="form-horizontal">
<div class="row" style="margin-left:0px">
<div>
<label for="SearchInput" style="font-size:18px">@Res.Search @Res.Week</label>
@Html.Editor("Search",new { htmlAttributes = new { @class = "form-control",@autofocus = "autofocus",@id = "SearchInput",@onkeyup = "myFunction()" } })
</div>
<div style="margin-left:10px;margin-top:18px">
<a href="@Url.Action("ResetDeadlines")" class="customBtnXSmall">Reset Deadlines</a>
</div>
</div>
</div>
}
这是最后期限类：
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Web;
namespace MyProject.Models.DBModels
{
public class Canteen_Deadlines
{
[Key]
public long? N { get; set; } //Number of days into the year (16th of January is 16 days into the year,so N would be = 16)
[Column(TypeName = "smalldatetime")]
public DateTime? DeadlineDate { get; set; }
public byte? WeekNo { get; set; }
public byte? MonthNo { get; set; }
public byte? QuarterNo { get; set; }
public short YearNo { get; set; }
public byte? DayofWeek { get; set; }
public bool? LastDowInMonth { get; set; } //Last DayOfWeek In Month
public byte? DoWAsc { get; set; } //DayOfWeek Ascending
}
}
解决方法
尝试使用此代码：
.....
var deadlines=new List<PP_CanteenScreen_Deadlines>();
for (var i = 1; i < 53; i++)
{
if (i == 1)
year += 1;
else
year = DateTime.Now.Year;
deadlineDate = GetThursdayOfWeek(year,i).AddDays(-7); //Gets the thursday
//of the week before,because that is the deadline for that week.
weekOfMonth = monthOfLastWeek < deadlineDate.Month ? 1 : weekOfMonth + 1;
var newDeadline = new PP_CanteenScreen_Deadlines
{
N = DaysFromNewYear(year,deadlineDate),DeadlineDate = deadlineDate,WeekNo = (byte)i,MonthNo = (byte)deadlineDate.Month,QuarterNo = (byte)GetQuarterNumber(deadlineDate.Month),YearNo = (short)year,DayofWeek = 4,LastDowInMonth = IsLastDoWInMonth(deadlineDate),DoWAsc = (byte)weekOfMonth
};
deadlines.Add(newDeadline);
monthOfLastWeek = deadlineDate.Month;
}
db.PP_CanteenScreen_Deadlines.AddRange(deadlines);
var result= db.SaveChanges();
if(result < 52) .....your error code
........
我想知道你为什么不尝试使用自动增量主键而不是 公长？否特别是我不喜欢您的主键可以为空。这有什么原因吗？
,经过多次尝试找出真正的问题并在@Sergey 的大力协助下，我意识到根本问题是由于数据库中表的设计以及 Entity Framework 6 的工作方式造成的。
解决方案：
我在代码中的 Canteen_Deadlines 类中添加了一个属性 ID，它现在是键，并在数据库表设计器中添加了相应的列。 EF6 现在知道我正在添加新行并让数据库表分配 ID，因此我可以分配自己的 N 个值。
背景：
EF6 一直表现得好像我在尝试更新我的行，因为 N 是我在 EF6 中的键，如果不是因为我正在尝试添加行，这将是有意义的。使用 Microsoft 文档在 Try-Catch 上执行 UpdateConcurrencyException 确认它正在尝试更新行，但在我实际添加行时无法执行此操作（新的异常是说捕获逻辑会不适用于处于“已添加”状态的实体）。
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