EF多对多关系未为其中一个实体添加记录

所以我在看这本书 Entity Framework 6 Recipes 。我正在使用 Visual Studio 2017 ,则, .NET 4.6.1 和 EF 6.2.0 。

我创建了这个简单的DB结构:

CREATE TABLE Album
(
    AlbumId INT IDENTITY(1,1) NOT NULL,
    AlbumName NVARCHAR(100) NOT NULL,
    CONSTRAINT [PK_Album] PRIMARY KEY CLUSTERED ([AlbumId] ASC)
)

CREATE TABLE Artist
(
    ArtistId INT IDENTITY(1,1) NOT NULL,
    FirstName NVARCHAR(100) NOT NULL,
    MiddleName NVARCHAR(100) NOT NULL,
    LastName NVARCHAR(100) NOT NULL,
    CONSTRAINT [PK_Artist] PRIMARY KEY CLUSTERED (ArtistId ASC)
)

CREATE TABLE LinkTable
(
    ArtistId INT NOT NULL,
    AlbumId INT NOT NULL,
    CONSTRAINT FK_LinkTable_Artist FOREIGN KEY (ArtistId) REFERENCES dbo.Artist (ArtistId),
    CONSTRAINT FK_LinkTable_Album FOREIGN KEY (AlbumId) REFERENCES dbo.Album (AlbumId)
)
ALTER TABLE LinkTable ADD CONSTRAINT PK_LinkTable PRIMARY KEY (ArtistId, AlbumId)

在代码中我有:

static void Main(string[] args)
{
    SeedMusicData();    
    ListMusicData();
}

问题是当我尝试向数据库添加新记录时。如果在 SeedMusicData() 我有这个:

private static void SeedMusicData()
{
    using (var context = new MusicEntities())
    {
        var artist = new Artist { FirstName = "Alan", LastName = "Jackson", MiddleName = "X." };
        var album1 = new Album { AlbumName = "Drive" };
        var album2 = new Album { AlbumName = "Live at Texas stadium" };

        artist.Albums.Add(album1);
        artist.Albums.Add(album2);

        context.Artists.Add(artist);
        context.SaveChanges();
    }
}

然后一切正常,数据存储在数据库中。

但是,如果我尝试这样做:

private static void SeedMusicData()
{
    using (var context = new MusicEntities())
    {
        var artist1 = new Artist { FirstName ="Tobby", LastName = "Keith", MiddleName = "Y." };
        var artist2 = new Artist { FirstName = "Merle", LastName = "Haggard", MiddleName = "Z." };
        var album = new Album { AlbumName = "Hokytonk University"};
        artist1.Albums.Add(album);
        artist2.Albums.Add(album);

        context.Albums.Add(album); //use Albums instead Artists when it works

        context.SaveChanges();
    }
}

然后数据库中没有存储任何内容,我也没有遇到任何异常。我想除了这本书之外,我一直在遵循这本书:

ALTER TABLE LinkTable ADD CONSTRAINT PK_LinkTable PRIMARY KEY (ArtistId, AlbumId)

由于我得到的错误似乎是由于缺少连接表的主键引起的,在添加一个主键后,错误得到了修复。但我想知道这是否是问题的原因。

P、 S

因此,一些其他信息:

这是模型在VS designer中的外观:

和内部 Music.tt 我有:

专辑cs:

public partial class Album
    {
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
        public Album()
        {
            this.Artists = new HashSet<Artist>();
        }

        public int AlbumId { get; set; }
        public string AlbumName { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<Artist> Artists { get; set; }
    }

和艺术家。cs:

public partial class Artist
    {
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
        public Artist()
        {
            this.Albums = new HashSet<Album>();
        }

        public int ArtistId { get; set; }
        public string FirstName { get; set; }
        public string MiddletName { get; set; }
        public string LastName { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<Album> Albums { get; set; }
    }

连接表在数据库中,但据我所知,如果它只包含两个外键,则EF应该不包含它。