以下是我希望在拥有歌曲专辑的网站中拥有的2个课程，但我不确定如何使用种子方法。我已经就这个问题进行了非常广泛的阅读，但到目前为止我还没有发现这种情况。这可以通过不将Album作为属性轻松解决，因为我可以先播放歌曲，但我真的想要Album属性。事实上，如果我可以消除albumId并且只拥有Album属性，那也会很好，尽管我不确定如果没有albumId属性将如何强制执行外键关系。 我确信有一个简单的答案，但我很惊讶它很难找到一个例子。 所以这是我想要的2个课程：
public class Album
{
public Album()
{
Songs = new List<Song>();
}
public int AlbumId { get; set; }
public int ReleaseYear { get; set; }
public int NumberOfTracks { get; set; }
public string Artist { get; set; }
public string Name { get; set; }
public ICollection<Song> Songs { get; set; }
}
public class Song
{
public int SongId { get; set; }
public int TrackNumber { get; set; }
public string Name { get; set; }
public List<string> Composers { get; set; }
public List<string> FeaturedArtists { get; set; }
public List<string> Producers { get; set; }
public Album Album { get; set; }
public int? AlbumId { get; set; }
}
这是我不完整的种子方法：
protected override void Seed(IQsLab.Models.ApplicationDbContext context)
{
context.Albums.AddOrUpdate(
p => p.Artist,
new Album {
Artist = "Linguistics",
Name = "The Writes of Passage",
NumberOfTracks = 17,
ReleaseYear = 2007,
AlbumId = 1,
Songs = new List<Song>()
{
new Song{
TrackNumber = 1,
AlbumId = 1,
Album = ??????????????????????????????????????,
Name = "Glory",
Composers = new List<string>(){
"Bobby Ruckuss"
},
Producers = new List<string>(){
"Bobby Ruckuss"
},
FeaturedArtists = new List<string>{
"Dj Solo",
"DJ Step 1"
}
},
new Song{
TrackNumber = 2,
Name = "Children of Atlantis",
Composers = new List<string>(){
"Bobby Ruckuss"
},
Producers = new List<string>(){
"Bobby Ruckuss"
}
},
new Song{
TrackNumber = 3,
Name = "On the Grind",
Composers = new List<string>(){
"Dan Kemp"
},
Producers = new List<string>(){
"Dan Kemp"
}
},
new Song{
TrackNumber = 4,
Name = "No Turnin Back",
Composers = new List<string>(){
"Bobby Ruckuss"
},
Producers = new List<string>(){
"Bobby Ruckuss"
},
FeaturedArtists = new List<string>{
"Tassa"
}
},
new Song{
TrackNumber = 5,
Name = "How Many",
Composers = new List<string>(){
"Bobby Ruckuss"
},
Producers = new List<string>(){
"Bobby Ruckuss"
}
},
new Song{
TrackNumber = 6,
Name = "Have Faith",
Composers = new List<string>(){
"Dan Kemp"
},
Producers = new List<string>(){
"Dan Kemp"
}
},
new Song{
TrackNumber = 7,
Name = "Mozart's Finest",
Composers = new List<string>(){
"Bobby Ruckuss"
},
Producers = new List<string>(){
"Bobby Ruckuss"
},
FeaturedArtists = new List<string>{
"Dj Solo",
"2Mex"
}
},
new Song{
TrackNumber = 8,
Name = "The Museum",
Composers = new List<string>(){
"Dan Kemp"
},
Producers = new List<string>(){
"Dan Kemp"
},
FeaturedArtists = new List<string>{
"DJ 3rdi"
}
},
new Song{
TrackNumber = 9,
Name = "Broken Tongues",
Composers = new List<string>(){
"Anno Domini"
},
Producers = new List<string>(){
"Anno Domini"
}
},
new Song{
TrackNumber = 10,
Name = "Politics",
Composers = new List<string>(){
"Kasper"
},
Producers = new List<string>(){
"Kasper"
}
},
new Song{
TrackNumber = 11,
Name = "The Music Is Ours",
Composers = new List<string>(){
"Bobby Ruckuss"
},
Producers = new List<string>(){
"Bobby Ruckuss"
}
},
new Song{
TrackNumber = 12,
Name = "It's Us",
Composers = new List<string>(){
"Bobby Ruckuss"
},
Producers = new List<string>(){
"Bobby Ruckuss"
},
FeaturedArtists = new List<string>{
"2Mex"
}
},
new Song{
TrackNumber = 13,
Name = "Where Did Hip-hop Go?",
Composers = new List<string>(){
"Dan Kemp"
},
Producers = new List<string>(){
"Dan Kemp"
}
},
new Song{
TrackNumber = 14,
Name = "Tha Realness",
Composers = new List<string>(){
"Kasper"
},
Producers = new List<string>(){
"Kasper"
}
},
new Song{
TrackNumber = 15,
Name = "How To Make It",
Composers = new List<string>(){
"Bobby Ruckuss"
},
Producers = new List<string>(){
"Bobby Ruckuss"
}
},
new Song{
TrackNumber = 16,
Name = "A Warrior's Ballad",
Composers = new List<string>(){
"Bobby Ruckuss"
},
Producers = new List<string>(){
"Bobby Ruckuss"
},
FeaturedArtists = new List<string>{
"Tassa"
}
},
new Song{
TrackNumber = 17,
Name = "Multiple Choice",
Composers = new List<string>(){
"Bobby Ruckuss"
},
Producers = new List<string>(){
"Bobby Ruckuss"
}
}
}
}
);
}
基本上，我如何设置Album = thisAlbumImCreatingRightNow，？
答案 0 :(得分：0)
您只需创建相册和歌曲，设置它们之间的关系并调用保存更改。 DbContext将自动为您完成剩余的工作（更改跟踪/关系修正）。这就是ORM有趣的原因;
protected override void Seed(IQsLab.Models.ApplicationDbContext context)
{
Album album1 = new Album { /* ... */ };
Album album2 = new Album { /* ... */ };
Album album3 = new Album { /* ... */ };
Song1_1 = new Song { /* ... */ };
Song1_2 = new Song { /* ... */ };
Song1_3 = new Song { /* ... */ };
// ...
Album1.Songs.Add(Song1_1);
Album1.Songs.Add(Song1_2);
Album1.Songs.Add(Song1_3);
// ...
context.Albums.Add(Album1);
context.Albums.Add(Album2);
context.Albums.Add(Album3);
// ...
context.SaveChanges();
}
注意1：context.Albums.Add(AlbumN)方法不仅将AlbumN附加到db上下文，还附加所有子项。他们都获得了州Added。
注意2：当你致电SaveChanges时，EF会注意恢复实体的PK（例如Album1）并修复所有相关孩子的关系。在这种情况下，这意味着在插入Song1_*时将所有Album1的FK设置为已恢复的PK。
顺便说一句，除非您另外配置，否则默认的EF约定将在数据库中将int PK实现为标识，因此它们将自动生成。我假设你没有使用属性，Fluent API或自定义约定来调整你的模型。
所以，它比你想象的容易得多。