使用 EF CPT5 进行域建模和映射

我正在尝试制作一个包含照片集的相册的模型。每个相册都会有一组照片和一张拇指照片。这是我拥有的，但 EF 似乎不喜欢它。我正在使用 EF CPT5

该模型:

public class Album : IEntity {
  private DateTime _dateCreated;
  public Album() {
    _dateCreated = SystemTime.Now();
    Photos = new List<Photo>();
  }

  public long Id { get; set; }
  public string Name { get; set; }
  public string Location { get; set; }
  public DateTime DateCreated {  get { return _dateCreated; }  set { _dateCreated = value; } }

  public virtual Site Site { get; set; }
  public virtual Photo Thumbnail { get; set; }
  public long ThumbnailId { get; set; }
  public virtual ICollection<Photo> Photos { get; set; }
 }



public class Photo : IEntity {
  public Photo() {
    _dateCreated = SystemTime.Now();
  }
  private DateTime _dateCreated;
  public long Id { get; set; }
  public string Caption { get; set; }
  public string FileName { get; set; }
  public DateTime DateCreated<br/>{ get { return _dateCreated; } set { _dateCreated = value; } }
  public long AlbymId { get; set; }
  public virtual Album Album { get; set; }
 }

映射代码：

public class AlbumMap : EntityTypeConfiguration<Album> {
  public AlbumMap() {
    HasRequired(x => x.Thumbnail).WithMany().HasForeignKey(a => a.ThumbnailId).WillCascadeOnDelete(false);
        Property(x => x.Location).IsVariableLength().HasMaxLength(80);
        Property(x => x.Name).IsVariableLength().HasMaxLength(80).IsRequired();
    }
 }

 public class PhotoMap : EntityTypeConfiguration<Photo> {
  public PhotoMap() {
    HasRequired(p => p.Album).WithMany(a => a.Photos).HasForeignKey(p => p.AlbymId);
    Property(x => x.FileName).IsVariableLength().HasMaxLength(255).IsRequired();
    Property(x => x.Caption).IsVariableLength().HasMaxLength(255);
    Property(x => x.DateCreated);
    ToTable("SiteAlbumPhotos");
    }
 }

Context

public class Database : ObjectContext {

        public Database(EntityConnection connection) : base(connection) {
            ContextOptions.LazyLoadingEnabled = true;
            ContextOptions.ProxyCreationEnabled = true;
        }

        private IObjectSet<User> _users;
        private IObjectSet<Site> _sites;
        private IObjectSet<SiteDonation> _donations;
        private IObjectSet<SiteAnnouncement> _siteAnnouncements;
        private IObjectSet<SiteData> _siteData;
        private IObjectSet<SiteLink> _siteLinks;
        private IObjectSet<SitePost> _sitePosts;
        private IObjectSet<Theme> _theme;
        private IObjectSet<Album> _siteAlbums;
        private IObjectSet<Photo> _siteAlbumPhotos;
        private IObjectSet<CommunityPost> _communityPosts;
        private IObjectSet<CommunityComment> _communityComments;

        public IObjectSet<User> Users {
            get{ return _users ?? (_users = ObjectSet<User>()); }
        }
        public IObjectSet<Album> SiteAlbums {
            get { return _siteAlbums ?? (_siteAlbums =  ObjectSet<Album>()); }
        }
        public IObjectSet<Photo> SiteAlbumsPhotos {
            get { return _siteAlbumPhotos ?? (_siteAlbumPhotos = ObjectSet<Photo>()); }
        }
        public IObjectSet<Site> Sites {
            get{ return _sites ?? (_sites = ObjectSet<Site>()); }
        }

        public IObjectSet<SiteDonation> SiteDonations {
            get { return _donations ?? (_donations = ObjectSet<SiteDonation>()); }
        }

        public IObjectSet<SiteAnnouncement> SiteAnnouncements {
            get { return _siteAnnouncements ?? (_siteAnnouncements = ObjectSet<SiteAnnouncement>()); }
        }

        public IObjectSet<SiteData> SiteData {
            get { return _siteData ?? (_siteData = ObjectSet<SiteData>()); }
        }

        public IObjectSet<SiteLink> SiteLinks {
            get { return _siteLinks ?? (_siteLinks = ObjectSet<SiteLink>()); }
        }

        public IObjectSet<SitePost> SitePosts {
            get { return _sitePosts ?? (_sitePosts = ObjectSet<SitePost>()); }
        }

        public IObjectSet<Theme> Themes { 
            get { return _theme ?? (_theme = ObjectSet<Theme>()); }
        }
        public IObjectSet<CommunityPost> CommunityPosts {
            get { return _communityPosts ?? (_communityPosts = ObjectSet<CommunityPost>()); }
        }
        public IObjectSet<CommunityComment> CommunityComments {
            get { return _communityComments ?? (_communityComments = ObjectSet<CommunityComment>()); }
        }

        public virtual IObjectSet<T> ObjectSet<T>() where T : class, IEntity {
            return CreateObjectSet<T>();
        }
        public virtual void Commit() {
            SaveChanges();
        }
    }

数据库工厂

public class DatabaseFactory : Disposable, IDatabaseFactory
    {
        private static readonly ModelBuilder builder = CreateBuilder();
        private readonly DbProviderFactory _providerFactory;
        private readonly string _connectionString;
        private Database _database;
        //
        public DatabaseFactory(DbProviderFactory providerFactory, string connectionString)
        {
            Check.Argument.IsNotNull(providerFactory, "providerFactory");
            Check.Argument.IsNotNullOrEmpty(connectionString, "connectionString");
            _providerFactory = providerFactory;
            _connectionString = connectionString;
        }
        //
        public Database Get()
        {
            if(_database == null)
            {
                var connection = _providerFactory.CreateConnection();
                connection.ConnectionString = _connectionString;
                //_database = builder.CreateModel(connection); LEG 1 CPT 3
                //var ctx = dbModel.CreateObjectContext<ObjectContext>(_connectionString); LEG 1 CPT 3
                //var modelBuilder = builder.CreateModel(); LEG 2 CPT 4
                //_database = modelBuilder.CreateObjectContext<Database>(connection); LEG 2 CPT 4
                //_database = modelBuilder.CreateObjectContext<Database>(connection); LEG 2 CPT 4
                var modelBuilder = builder.Build(connection);
                var dbModel = new DbModel(modelBuilder);
                _database = dbModel.CreateObjectContext<Database>(connection);

            }

            return _database;
        }
        //
        protected override void DisposeCore()
        {
            if (_database != null)
            {
                _database.Dispose();
            }
        }
        //
        private static ModelBuilder CreateBuilder()
        {
            //ContextBuilder<Database> contextBuilder = new ContextBuilder<Database>();
            var contextBuilder = new ModelBuilder();
            //IEnumerable<Type> configurationTypes = typeof(DatabaseFactory)
            //    .Assembly
            //    .GetTypes()
            //    .Where(type => type.IsPublic && type.IsClass && !type.IsAbstract && !type.IsGenericType && typeof(StructuralTypeConfiguration).IsAssignableFrom(type) && (type.GetConstructor(Type.EmptyTypes) != null));

            //foreach (StructuralTypeConfiguration configuration in configurationTypes.Select(type => (StructuralTypeConfiguration)Activator.CreateInstance(type)))
            //{
            //    contextBuilder.Configurations.Add(configuration);
            //}
            contextBuilder.Configurations.Add(new CommunityCommentMap());
            contextBuilder.Configurations.Add(new CommunityPostMap());
            contextBuilder.Configurations.Add(new SiteAlbumMap());
            contextBuilder.Configurations.Add(new SiteAlbumPhotoMap());
            contextBuilder.Configurations.Add(new SiteAnnouncementMap());
            contextBuilder.Configurations.Add(new SiteDataMap());
            contextBuilder.Configurations.Add(new SiteDonationMap());
            contextBuilder.Configurations.Add(new SiteLinkMap());
            contextBuilder.Configurations.Add(new SiteMap());
            contextBuilder.Configurations.Add(new SitePostMap());
            contextBuilder.Configurations.Add(new ThemeMap());
            contextBuilder.Configurations.Add(new UserMap());
            return contextBuilder;
        }
    }

我是否正确建模和映射？我需要能够在不指定缩略图的情况下创建新相册。截至目前，一切正常，直到我尝试添加缩略图，然后出现此错误：

System.Data.UpdateException：无法确定相关操作的有效顺序。由于外键约束、模型要求或存储生成的值，可能会存在依赖关系。

在 System.Data.Mapping.Update.Internal.UpdateTranslator.DependencyOrderingError（IEnumerable`1 余数） 在 System.Data.Mapping.Update.Internal.UpdateTranslator.ProduceCommands() 在 System.Data.Mapping.Update.Internal.UpdateTranslator.Update（IEntityStateManager stateManager，IEntityAdapter 适配器） 在 System.Data.Objects.ObjectContext.SaveChanges（SaveOptions 选项） 在 Database.cs 中的 PostHope.Infrastruct.DataAccess.Database.Commit() 处：第 74 行 在 BuildDatabase.cs 中的 PostHope.Infrastruct.DataAccess.IntegrationTests.BuildDatabase.Add_test_data_to_database() 处：第 252 行

任何帮助都会很棒！

我们通过 EF CTP4 解决了这个问题here https://stackoverflow.com/questions/4355998/domain-modeling-question-using-c-with-entity-framework-ctp-4/4359593#4359593。现在这是 EF CTP5 的更新，已发布released http://blogs.msdn.com/b/adonet/archive/2010/12/06/ef-feature-ctp5-released.aspx今天早些时候。

public class Photo 
{
    public long PhotoId { get; set; }        
    [MaxLength(255)]
    public string Caption { get; set; }        
    [MaxLength(255)][Required]
    public string FileName { get; set; }        
    public DateTime DateCreated { get; set; }
    public long AlbumId { get; set; }        
    public virtual Album Album { get; set; }
}

[Table("SiteAlbumPhotos")]
public class Album 
{
    public long AlbumId { get; set; }        
    [MaxLength(80)][Required]
    public string Name { get; set; }        
    [MaxLength(80)]
    public string Location { get; set; }        
    public DateTime DateCreated { get; set; }                
    public long ThumbnailId { get; set; }                
    public virtual Photo Thumbnail { get; set; }                
    public virtual ICollection<Photo> Photos { get; set; }
}  

public class PhotoMap : EntityTypeConfiguration<Photo> {
    public PhotoMap() {            
        HasRequired(p => p.Album).WithMany(a => a.Photos)
                                 .HasForeignKey(p => p.AlbumId);
    }
}

public class AlbumMap : EntityTypeConfiguration<Album> {
    public AlbumMap() {
        HasRequired(a => a.Thumbnail).WithMany()
                                     .HasForeignKey(a => a.ThumbnailId)
                                     .WillCascadeOnDelete(false);
    }
}

public class MyContext : DbContext {
    public DbSet<Photo> Photos { get; set; }
    public DbSet<Album> Albums { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder) {
        modelBuilder.Configurations.Add<Photo>(new PhotoMap());
        modelBuilder.Configurations.Add<Album>(new AlbumMap());
    }
}

Which results to this DB schema: