几周以来，我一直在 .NET 4.0 解决方案中使用实体框架。它是 EF 4.3.1。我首先创建了数据库架构，并使用“EF4.x DbContext Generator”模板生成了我的实体对象。
我在架构中有三个表，并且使用简单的 CRUD 方法都可以正常工作。
我现在添加了第四个表“Subjects”，它有一个对现有表“SourceUri”的外键引用，这样一个 SourceUri 可以有 0 个主题，而一个主题只有一个 SourceUri。
我已经更新了我的 edmx 模型，它看起来是正确的。但是，无论我尝试什么，我似乎都无法执行以下操作：
- 添加新的 SourceUri 记录
- 为新的 SourceUri 添加一个或多个主题
这是我目前正在尝试的代码。您可以看到我定期保存上下文，但最初我只在方法结束时保存更改一次。
/// <summary>
/// Adds a new Source URI to the system
/// </summary>
/// <param name="sourceUri">The source URI to add</param>
/// <param name="subjectNames">List of subjects for this source URI, in order</param>
/// <returns>The added source URI</returns>
public SourceUri AddSourceUri(SourceUri sourceUri, IList<string> subjectNames)
{
try
{
_logger.Debug("Adding new source URI '{0}', with '{1}' subjects.", sourceUri.Uri,
subjectNames != null ? subjectNames.Count : 0);
LogSourceUriDetails(sourceUri, "Adding");
using (var dbContext = GetDbContext())
{
dbContext.SourceUris.Add(sourceUri);
dbContext.SaveChanges(); // this save succeeds
// add the subjects if there are any
if (subjectNames != null)
{
for (int i = 0; i < subjectNames.Count; i++)
{
Subject newSubject = new Subject()
{
DisplayOrder = i,
SourceUriId = sourceUri.SourceUriId,
SubjectText = subjectNames.ElementAt(i).Trim()
};
_logger.Debug("Adding new subject '{0}' to source URI '{1}'.", newSubject.SubjectText,
sourceUri.Uri);
dbContext.Subjects.Add(newSubject); // this line fails
dbContext.SaveChanges();
}
}
_logger.Debug("Successfully added new source URI '{0}' with '{1}' subjects. Source URI ID is '{2}'.",
sourceUri.Uri, subjectNames != null ? subjectNames.Count : 0, sourceUri.SourceUriId);
return sourceUri;
}
}
catch (Exception exception)
{
_logger.ErrorException(string.Format("An error occurred adding new source URI '{0}' with '{1}' subjects.",
sourceUri.Uri, subjectNames != null ? subjectNames.Count : 0), exception);
throw;
}
}
代码添加新的 SourceUri 并保存更改。但是，它无法将新的主题添加到数据上下文中。它并没有达到试图保存该更改的程度。
例外是：
Unable to set field/property Subjects on entity type CommentService.DomainObjects.SourceUri. See InnerException for details.
System.Data.Objects.Internal.PocoPropertyAccessorStrategy.CollectionRemove(RelatedEnd relatedEnd, Object value)
System.Data.Objects.Internal.EntityWrapper`1.CollectionRemove(RelatedEnd relatedEnd, Object value)
System.Data.Objects.DataClasses.EntityCollection`1.RemoveFromObjectCache(IEntityWrapper wrappedEntity)
System.Data.Objects.DataClasses.RelatedEnd.Remove(IEntityWrapper wrappedEntity, Boolean doFixup, Boolean deleteEntity, Boolean deleteOwner, Boolean applyReferentialConstraints, Boolean preserveForeignKey)
System.Data.Objects.DataClasses.RelatedEnd.FixupOtherEndOfRelationshipForRemove(IEntityWrapper wrappedEntity, Boolean preserveForeignKey)
System.Data.Objects.DataClasses.RelatedEnd.Remove(IEntityWrapper wrappedEntity, Boolean doFixup, Boolean deleteEntity, Boolean deleteOwner, Boolean applyReferentialConstraints, Boolean preserveForeignKey)
System.Data.Objects.DataClasses.EntityReference`1.Exclude()
System.Data.Objects.DataClasses.RelationshipManager.RemoveRelatedEntitiesFromObjectStateManager(IEntityWrapper wrappedEntity)
System.Data.Objects.ObjectContext.AddObject(String entitySetName, Object entity)
System.Data.Entity.Internal.Linq.InternalSet`1.<>c__DisplayClass5.<Add>b__4()
System.Data.Entity.Internal.Linq.InternalSet`1.ActOnSet(Action action, EntityState newState, Object entity, String methodName)
System.Data.Entity.Internal.Linq.InternalSet`1.Add(Object entity)
System.Data.Entity.DbSet`1.Add(TEntity entity)
CommentService.Business.Managers.SourceUriManager.AddSourceUri(SourceUri sourceUri, IList`1 subjectNames) in C:\Projects\SVN Misc Projects\CommentService\trunk\CommentService.Business\Managers\SourceUriManager.cs:line 152
CommentService.Web.Comment.AddSourceUri(SourceUri sourceUri, IList`1 subjectNames) in C:\Projects\SVN Misc Projects\CommentService\trunk\CommentService.Web\Comment.svc.cs:line 173
SyncInvokeAddSourceUri(Object , Object[] , Object[] )
System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object[] inputs, Object[]& outputs)
System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc& rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage41(MessageRpc& rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage4(MessageRpc& rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage31(MessageRpc& rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage3(MessageRpc& rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage2(MessageRpc& rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage11(MessageRpc& rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage1(MessageRpc& rpc)
System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)
我在这个问题上转了一圈又一圈，看到了几个略有不同的例外。他们似乎都指出 SourceUri 对象的 Subjects 导航属性在某种程度上是只读的或固定长度（数组？）。
生成的实体类如下所示：
//------------------------------------------------------------------------------
// <auto-generated>
// This code was generated from a template.
//
// Manual changes to this file may cause unexpected behavior in your application.
// Manual changes to this file will be overwritten if the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------
namespace CommentService.DomainObjects
{
using System;
using System.Collections.Generic;
public partial class SourceUri
{
public SourceUri()
{
this.Comments = new HashSet<Comment>();
this.Subjects = new HashSet<Subject>();
}
public long SourceUriId { get; set; }
public string Uri { get; set; }
public string Description { get; set; }
public System.DateTime DateCreated { get; set; }
public string AdminUser { get; set; }
public virtual ICollection<Comment> Comments { get; set; }
public virtual ICollection<Subject> Subjects { get; set; }
}
}
//------------------------------------------------------------------------------
// <auto-generated>
// This code was generated from a template.
//
// Manual changes to this file may cause unexpected behavior in your application.
// Manual changes to this file will be overwritten if the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------
namespace CommentService.DomainObjects
{
using System;
using System.Collections.Generic;
public partial class Subject
{
public Subject()
{
this.Comments = new HashSet<Comment>();
}
public long SubjectId { get; set; }
public long SourceUriId { get; set; }
public string SubjectText { get; set; }
public int DisplayOrder { get; set; }
public virtual ICollection<Comment> Comments { get; set; }
public virtual SourceUri SourceUri { get; set; }
}
}
为什么这不起作用？
我检查过/尝试过的事情的快速列表：
- 数据库架构看起来正确 - 我可以使用 SQL 和主键按预期插入记录，外键和身份似乎表现正确
- 该模型似乎正确反映了数据库架构，包括 PK 身份（EntityKey = true，StoreGeneratedPattern=Identity）
- 我已经设法让 EF 将数据持久保存到我的架构中，但是在插入数据后，会引发异常，指出上下文可能不同步 - 再次与无法更新 SourceUri 对象的主题导航属性有关
- 我尝试将主题添加到 dbContext.Subjects 集合以及 SourceUri.Subjects 集合。我还尝试设置主题的 SourceUri 属性而不是主题的 SourceUriId 属性。