Entity framework 将持久化对象附加到新对象的实体框架

我正在尝试执行一项非常简单的任务，即“在数据库中添加具有角色的用户”。这些角色已填充到数据库中，我只是将该角色添加到用户角色集合中，但它一直引发以下异常：

------ Test started: Assembly: EStudy.Repositories.TestSuite.dll ------

TestCase 'EStudy.Repositories.TestSuite.Repositories.when_saving_new_user.should_save_user_with_role_successfully'
failed: System.InvalidOperationException : The EntityKey property can only be set when the current value of the property is null.
 at System.Data.Objects.EntityEntry.GetAndValidateChangeMemberInfo(String entityMemberName, Object complexObject, String complexObjectMemberName, StateManagerTypeMetadata& typeMetadata, String& changingMemberName, Object& changingObject)
 at System.Data.Objects.EntityEntry.EntityMemberChanging(String entityMemberName, Object complexObject, String complexObjectMemberName)
 at System.Data.Objects.EntityEntry.EntityMemberChanging(String entityMemberName)
 at System.Data.Objects.ObjectStateEntry.System.Data.Objects.DataClasses.IEntityChangeTracker.EntityMemberChanging(String entityMemberName)
 at System.Data.Objects.DataClasses.EntityObject.set_EntityKey(EntityKey value)
 at System.Data.Objects.Internal.LightweightEntityWrapper`1.set_EntityKey(EntityKey value)
 at System.Data.Objects.ObjectStateManager.AddEntry(IEntityWrapper wrappedObject, EntityKey passedKey, EntitySet entitySet, String argumentName, Boolean isAdded)
 at System.Data.Objects.ObjectContext.AddSingleObject(EntitySet entitySet, IEntityWrapper wrappedEntity, String argumentName)
 at System.Data.Objects.DataClasses.RelatedEnd.AddEntityToObjectStateManager(IEntityWrapper wrappedEntity, Boolean doAttach)
 at System.Data.Objects.DataClasses.RelatedEnd.AddGraphToObjectStateManager(IEntityWrapper wrappedEntity, Boolean relationshipAlreadyExists, Boolean addRelationshipAsUnchanged, Boolean doAttach)
 at System.Data.Objects.DataClasses.RelatedEnd.IncludeEntity(IEntityWrapper wrappedEntity, Boolean addRelationshipAsUnchanged, Boolean doAttach)
 at System.Data.Objects.DataClasses.EntityCollection`1.Include(Boolean addRelationshipAsUnchanged, Boolean doAttach)
 at System.Data.Objects.DataClasses.RelationshipManager.AddRelatedEntitiesToObjectStateManager(Boolean doAttach)
 at System.Data.Objects.ObjectContext.AddObject(String entitySetName, Object entity)
 C:\Projects\EStudy\EStudySolution\EStudy.BusinessObjects\Entities\EStudyModel.Designer.cs(97,0): at EStudy.BusinessObjects.Entities.EStudyDevDatabaseEntities.AddToUsers(User user)
 C:\Projects\EStudy\EStudySolution\EStudy.BusinessObjects\Repositories\UserRepository.cs(17,0): at EStudy.BusinessObjects.Repositories.UserRepository.Save(User user)
 C:\Projects\EStudy\EStudySolution\EStudy.Repositories.TestSuite\Repositories\Test_UserRepository.cs(47,0): at EStudy.Repositories.TestSuite.Repositories.when_saving_new_user.should_save_user_with_role_successfully()


0 passed, 1 failed, 0 skipped, took 6.07 seconds (NUnit 2.5).

仅当EntityKey属性的当前值为null时，才能设置该属性

以下是User.cs中的代码：

  public void AddRole(Role role)
        {
            if (!Exists(role))
            {
                 role.User = this;
                Roles.Add(role);                 
            }
        }

以下是失败的测试：

  [Test]        
        public void should_save_user_with_role_successfully() 
        {
            var _role = _roleRepository.GetByName("Student");                        

            _user.AddRole(_role); 

            _userRepository.Save(_user);

            Assert.IsTrue(_user.UserId > 0);             
        }

存储库代码：

  public bool Save(User user)
        {
            bool isSaved = false; 

            using (var db = new EStudyDevDatabaseEntities())
            {   
                db.AddToUsers(user);
                isSaved = db.SaveChanges() > 0;  
            }

            return isSaved; 

        }

以下是AddRole方法：

   public bool Exists(Role role)
        {
            var assignedRole = (from r in Roles
                                where r.RoleName.Equals(role.RoleName)
                                select r).SingleOrDefault();

            if (assignedRole != null) return true;

            return false; 
        }

        public void AddRole(Role role)
        {
            if (!Exists(role))
            {
                 role.User = this;
                Roles.Add(role);                 
            }
        }

以下是整个例外：

------ Test started: Assembly: EStudy.Repositories.TestSuite.dll ------

TestCase 'EStudy.Repositories.TestSuite.Repositories.when_saving_new_user.should_save_user_with_role_successfully'
failed: System.InvalidOperationException : The EntityKey property can only be set when the current value of the property is null.
 at System.Data.Objects.EntityEntry.GetAndValidateChangeMemberInfo(String entityMemberName, Object complexObject, String complexObjectMemberName, StateManagerTypeMetadata& typeMetadata, String& changingMemberName, Object& changingObject)
 at System.Data.Objects.EntityEntry.EntityMemberChanging(String entityMemberName, Object complexObject, String complexObjectMemberName)
 at System.Data.Objects.EntityEntry.EntityMemberChanging(String entityMemberName)
 at System.Data.Objects.ObjectStateEntry.System.Data.Objects.DataClasses.IEntityChangeTracker.EntityMemberChanging(String entityMemberName)
 at System.Data.Objects.DataClasses.EntityObject.set_EntityKey(EntityKey value)
 at System.Data.Objects.Internal.LightweightEntityWrapper`1.set_EntityKey(EntityKey value)
 at System.Data.Objects.ObjectStateManager.AddEntry(IEntityWrapper wrappedObject, EntityKey passedKey, EntitySet entitySet, String argumentName, Boolean isAdded)
 at System.Data.Objects.ObjectContext.AddSingleObject(EntitySet entitySet, IEntityWrapper wrappedEntity, String argumentName)
 at System.Data.Objects.DataClasses.RelatedEnd.AddEntityToObjectStateManager(IEntityWrapper wrappedEntity, Boolean doAttach)
 at System.Data.Objects.DataClasses.RelatedEnd.AddGraphToObjectStateManager(IEntityWrapper wrappedEntity, Boolean relationshipAlreadyExists, Boolean addRelationshipAsUnchanged, Boolean doAttach)
 at System.Data.Objects.DataClasses.RelatedEnd.IncludeEntity(IEntityWrapper wrappedEntity, Boolean addRelationshipAsUnchanged, Boolean doAttach)
 at System.Data.Objects.DataClasses.EntityCollection`1.Include(Boolean addRelationshipAsUnchanged, Boolean doAttach)
 at System.Data.Objects.DataClasses.RelationshipManager.AddRelatedEntitiesToObjectStateManager(Boolean doAttach)
 at System.Data.Objects.ObjectContext.AddObject(String entitySetName, Object entity)
 C:\Projects\EStudy\EStudySolution\EStudy.BusinessObjects\Entities\EStudyModel.Designer.cs(97,0): at EStudy.BusinessObjects.Entities.EStudyDevDatabaseEntities.AddToUsers(User user)
 C:\Projects\EStudy\EStudySolution\EStudy.BusinessObjects\Repositories\UserRepository.cs(17,0): at EStudy.BusinessObjects.Repositories.UserRepository.Save(User user)
 C:\Projects\EStudy\EStudySolution\EStudy.Repositories.TestSuite\Repositories\Test_UserRepository.cs(47,0): at EStudy.Repositories.TestSuite.Repositories.when_saving_new_user.should_save_user_with_role_successfully()


0 passed, 1 failed, 0 skipped, took 6.07 seconds (NUnit 2.5).

更新：

这是我的UserRepository和RoleRepository，它们都使用不同的上下文：

  public bool Save(User user)
        {
            bool isSaved = false; 

            using (var db = new EStudyDevDatabaseEntities())
            {              
                db.AddToUsers(user);
                isSaved = db.SaveChanges() > 0;  
            }

            return isSaved; 

        }

 public Role GetByName(string roleName)
        {
            using (var db = new EStudyDevDatabaseEntities())
            {
                return db.Roles.SingleOrDefault(x => x.RoleName.ToLower().Equals(roleName.ToLower())); 
            }           
        }

---

正如您所看到的，用户和角色正在使用您已经指出的不同上下文。使用单个datacontext的问题是我无法正确地分层应用程序

根据更新的问题再次更新

我不同意在存储库之间共享上下文时“不能正确分层应用程序”。这是一个你需要解决的问题，但它肯定是可以解决的。此外，我认为你会发现解决问题要比尝试使用多个上下文时产生的问题数量容易得多

无论如何，对于您的问题，实际上只有两种可能的解决方案：

手动跟踪特定实体附加到哪个上下文，并在必要时传输它（使用“附加”和“分离”）

在存储库实例之间共享上下文

在我们的ASP.NET MVC应用程序中，逻辑工作单元是单个请求。因此，我们在请求开始时实例化ObjectContext，在请求结束时处置它，并在创建新存储库时将其注入新存储库。存储库实例永远不会超过一个请求

根据更新的问题进行更新

角色存储库和用户存储库是否都有（单独的）上下文？下面是堆栈跟踪中发生的情况：

将用户添加到上下文中

RelationshipManager遍历用户并确保任何相关实体也在上下文中。其中包括设置其EntityKey属性

假定角色来自不同的上下文（情况似乎是这样，否则上下文应该检测到角色已经在上下文中），您应该看到一个错误，指示您无法将附加到一个上下文的实体添加到另一个上下文中。出于某种原因，你在这里看不到这一点。但无论如何，这不是一个有效的操作

相反，在分配角色的EntityKey时会出现错误

在我看来，一次使用一个ObjectContext应该是使用EntityFramework的一般规则。只有在你绝对被迫的情况下，你才应该使用多个上下文，根据我的经验，这几乎是不可能的。同时处理多个ObjectContext比一次处理一个要困难得多

好的，我不知道映射的细节，但我希望

AddRole

更符合以下内容：

public void AddRole(Role role)
{
    this.Roles.Add(role);
}

。。。如果用户->角色为。。或：

如果用户->角色为*.1

---

如果这没有帮助，请发布异常的堆栈跟踪。

这些ASP.NET FormsAuth用户和角色吗？不，只有表用户和角色（与身份验证无关的自定义表）。我更新了原始帖子！有用户表、角色表和用户角色。角色是预先填充的。UserRoles有UserId和RoleId。谢谢！我想我会选择HttpRequest，因为它是一个ASP.NETMVC应用程序。