实体框架4 CTP 5自我引用多对多

Question

我的数据库中有以下场景.这是一项研究记录,这些研究将其他研究作为先决条件.在我的数据库设计中,它看起来像这样:

我的代码看起来像这样:

public class Study
{
    public int ID { get; set; }
    public string Topic { get; set; }
    public byte TypeID { get; set; }
    public virtual StudyType Type { get; set; }
    public bool Deprecated { get; set; }

    public virtual ICollection<Study> Prerequisites { get; set; }
}

public class StudyType
{
    public byte ID { get; set; }
    public string Name { get; set; }

    public virtual ICollection<Study> Studies { get; set; }
}

public class MyContext : DbContext
{

    public DbSet<Study> Studies { get; set; }
    public DbSet<StudyType> StudyTypes { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Study>()
            .HasMany(p=>p.Prerequisites)
            .WithMany().Map(ps =>
                {
                    ps.ToTable("Prerequisites");
                    ps.MapLeftKey(x=>x.ID,"StudyID");
                    ps.MapRightKey(y=>y.ID,"PrerequisiteID");
                });
    }

我不是非常擅长EF语法,但从我发现谷歌搜索,似乎它应该工作.相反,我得到了Sequence contains more than one matching element.

我找到了这个,但由于实体引用自身,我无法仅在其中一个表中重命名关键字段:http://social.msdn.microsoft.com/Forums/eu/adonetefx/thread/745a2c4f- cb66-41ad-9524-15aa198c40c7

有人帮我解决了这个问题吗？

编辑

以下是异常的完整堆栈跟踪:

它在LINQ行上执行: var x = from s in db.Studies select s;

Server stack trace: 
 at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source, Func`2 predicate)
 at System.Data.Entity.ModelConfiguration.Configuration.Properties.Navigation.ManyToManyAssociationMappingConfiguration`2.Configure(DbAssociationSetMapping associationSetMapping)
 at System.Data.Entity.ModelConfiguration.Configuration.Properties.Navigation.NavigationPropertyConfiguration.Configure(DbDatabaseMapping databaseMapping)
 at System.Data.Entity.ModelConfiguration.Utilities.IEnumerableExtensions.Each[T](IEnumerable`1 ts, Action`1 action)
 at System.Data.Entity.ModelConfiguration.Configuration.Types.EntityTypeConfiguration.ConfigureAssociationMappings(DbDatabaseMapping databaseMapping)
 at System.Data.Entity.ModelConfiguration.Configuration.Types.EntityTypeConfiguration.Configure(DbEntityTypeMapping entityTypeMapping, DbDatabaseMapping databaseMapping, DbProviderManifest providerManifest)
 at System.Data.Entity.ModelConfiguration.Configuration.ModelConfiguration.Configure(DbDatabaseMapping databaseMapping, DbProviderManifest providerManifest)
 at System.Data.Entity.ModelConfiguration.ModelBuilder.Build(DbProviderManifest providerManifest, DbProviderInfo providerInfo, Boolean validateModel)
 at System.Data.Entity.ModelConfiguration.ModelBuilder.Build(DbConnection providerConnection)
 at System.Data.Entity.Internal.LazyInternalContext.CreateModel()
 at System.Lazy`1.CreateValue()

Exception rethrown at [0]: 
 at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source, Func`2 predicate)
 at System.Data.Entity.ModelConfiguration.Configuration.Properties.Navigation.ManyToManyAssociationMappingConfiguration`2.Configure(DbAssociationSetMapping associationSetMapping)
 at System.Data.Entity.ModelConfiguration.Configuration.Properties.Navigation.NavigationPropertyConfiguration.Configure(DbDatabaseMapping databaseMapping)
 at System.Data.Entity.ModelConfiguration.Utilities.IEnumerableExtensions.Each[T](IEnumerable`1 ts, Action`1 action)
 at System.Data.Entity.ModelConfiguration.Configuration.Types.EntityTypeConfiguration.ConfigureAssociationMappings(DbDatabaseMapping databaseMapping)
 at System.Data.Entity.ModelConfiguration.Configuration.Types.EntityTypeConfiguration.Configure(DbEntityTypeMapping entityTypeMapping, DbDatabaseMapping databaseMapping, DbProviderManifest providerManifest)
 at System.Data.Entity.ModelConfiguration.Configuration.ModelConfiguration.Configure(DbDatabaseMapping databaseMapping, DbProviderManifest providerManifest)
 at System.Data.Entity.ModelConfiguration.ModelBuilder.Build(DbProviderManifest providerManifest, DbProviderInfo providerInfo, Boolean validateModel)
 at System.Data.Entity.ModelConfiguration.ModelBuilder.Build(DbConnection providerConnection)
 at System.Data.Entity.Internal.LazyInternalContext.CreateModel()
 at System.Lazy`1.CreateValue()
 at System.Lazy`1.LazyInitValue()
 at System.Data.Entity.Internal.LazyInternalContext.InitializeContext()
 at System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType)
 at System.Data.Entity.Internal.Linq.InternalSet`1.Initialize()
 at System.Data.Entity.Internal.Linq.InternalSet`1.get_Provider()
 at System.Linq.Queryable.Select[TSource,TResult](IQueryable`1 source, Expression`1 selector)
 at DataAccess.Sql.SqlStudyRepository.GetAll() in C:\Side Work\Rephidim Church\Tuchikos 2011\Program\DataAccess\Sql\SqlStudyRepository.cs:line 22
 at API.Controllers.StudiesController.Index() in C:\Side Work\Rephidim Church\Tuchikos 2011\Program\API\Controllers\StudiesController.cs:line 24
 at lambda_method(Closure , ControllerBase , Object[] )
 at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
 at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
 at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClass15.<InvokeActionMethodWithFilters>b__12()
 at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)

Answer 1

这就是我在 EntityTypeConfiguration<> 实现中针对 CTP5 中类似情况的实现。

HasMany(g => g.SubGroups)
    .WithMany(g => g.ParentGroups)
    .Map(m => m.ToTable("Groups_SubGroups"));

不确定这如何转化为直接配置 DbContext，但我想它应该很接近。

如果没记错的话，CTP5 中并不存在 LeftKey() RightKey() 语法，因此您只需使用它创建或期望的默认列名称。就我而言，它是 GroupId 和 GroupId1。顺便说一下，它遵循模式 <class>Id 和 <class>Id1，而不是 <field> 和 <field>1。

您遇到的错误看起来确实很熟悉，而且我不记得解决方案在任何方面都是显而易见的。但是，我不久前确实把这一切都设置好了，所以我对如何实现有效的东西的记忆有点瑞士奶酪。希望它能帮助一些人。