c# - EF 代码优先 : Sequence contains more than one matching element

Question

我正在使用 EF6 代码优先，并且有一个 User需要与其他用户建立传入和传出连接的类。连接也有属性，所以我也有一个 Connections类。

public class User
{
    public int ID { get; set; }

    // Other properties removed here to keep it simple

    [InverseProperty("SourceUser")]
    public virtual ICollection<Connection> OutgoingConnections { get; set; }

    [InverseProperty("DestUser")]
    public virtual ICollection<Connection> IncomingConnections { get; set; }
}

public class Connection
{
    public int ID { get; set; }

    // Other properties removed here to keep it simple

    [InverseProperty("OutgoingConnections")]
    public User SourceUser { get; set; }

    [InverseProperty("IncomingConnections")]
    public User DestUser { get; set; }
}

更新数据库时出现以下错误。最初我没有 InverseProperty属性，所以我可以理解为什么 EF 在这种情况下不知道该怎么做。文档听起来这些属性是我想要的 - 但它仍然无法正常工作。也许我误会了。

我想以 Users 结尾表和一个 Connections Connections 所在的表表有 ID , SourceUserID , DestUserID (显然有 FK 约束)。

有什么想法吗？

Specify the '-Verbose' flag to view the SQL statements being applied to the target database. Applying explicit migrations: [201411192045091_InitialCreate]. Applying explicit migration: 201411192045091_InitialCreate. System.InvalidOperationException: Sequence contains more than one matching element at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable1 source,
Func2 predicate) at System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.<>c__DisplayClass250.b__247(<>f__AnonymousType2b2
<>h__TransparentIdentifier242) at
System.Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext()
at System.Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext()<br/>
at System.Collections.Generic.List1..ctor(IEnumerable1 collection)<br/>
at System.Linq.Enumerable.ToList[TSource](IEnumerable1 source) at System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.Diff(ModelMetadata source, ModelMetadata target, Lazy1 modificationCommandTreeGenerator,
MigrationSqlGenerator migrationSqlGenerator, String
sourceModelVersion, String targetModelVersion) at
System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.Diff(XDocument
sourceModel, XDocument targetModel, Lazy1 modificationCommandTreeGenerator, MigrationSqlGenerator migrationSqlGenerator, String sourceModelVersion, String targetModelVersion) at System.Data.Entity.Migrations.DbMigrator.IsModelOutOfDate(XDocument model, DbMigration lastMigration) at System.Data.Entity.Migrations.DbMigrator.Upgrade(IEnumerable1
pendingMigrations, String targetMigrationId, String lastMigrationId)<br/>
at
System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.Upgrade(IEnumerable1 pendingMigrations, String targetMigrationId, String lastMigrationId)
at System.Data.Entity.Migrations.DbMigrator.UpdateInternal(String targetMigration) at System.Data.Entity.Migrations.DbMigrator.<>c__DisplayClassc.b__b() at System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists(Action mustSucceedToKeepDatabase) at System.Data.Entity.Migrations.Infrastructure.MigratorBase.EnsureDatabaseExists(Action mustSucceedToKeepDatabase) at System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration) at System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update(String targetMigration) at System.Data.Entity.Migrations.Design.ToolingFacade.UpdateRunner.Run() at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate) at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
at System.Data.Entity.Migrations.Design.ToolingFacade.Run(BaseRunner runner) at System.Data.Entity.Migrations.Design.ToolingFacade.Update(String targetMigration, Boolean force) at System.Data.Entity.Migrations.UpdateDatabaseCommand.<>c__DisplayClass2.<.ctor>b__0() at System.Data.Entity.Migrations.MigrationsDomainCommand.Execute(Action command) Sequence contains more than one matching element

Answer 1

抱歉，如果需要使用 InverseProperties，但如果您可以灵活地以不同方式连接它们，则可以通过这种方式完成关系。

public class User
{
    public int ID { get; set; }

    [ForeignKey("ID")]
    public virtual ICollection<Connection> OutgoingConnections { get; set; }

    [ForeignKey("ID")]
    public virtual ICollection<Connection> IncomingConnections { get; set; }
}

public class Connection
{
    public int ID { get; set; }

    public int SourcerId {get;set;}

    public int DestUserId {get;set;}

    [ForeignKey("SourcerId")]
    public User SourceUser { get; set; }

     [ForeignKey("DestUserId")]
    public User DestUser { get; set; }
}

然后你需要添加配置。在我的例子中，为了测试这个，我在上下文中的 protected override void OnModelCreating(DbModelBuilder modelBuilder) 中做了它。

    modelBuilder.Entity<User>().HasMany(x=>x.IncomingConnections).WithRequired(x=>x.SourceUser).WillCascadeOnDelete(false);
    modelBuilder.Entity<User>().HasMany(x => x.OutgoingConnections).WithRequired(x => x.DestUser).WillCascadeOnDelete(false);