实体框架4.1代码优先的方式创建许多一对多的关系 [英] Entity Framework 4.1 Code First approach to create many-to-many relation
问题描述
我使用Silverlight的5测试版SDK和4.1的EntityFramework在Silverlight应用程序。
I'm using the Silverlight 5 Beta SDK and the EntityFramework 4.1 in an Silverlight Application.
我会尝试创建两个表作者和书'。在SQL中，应该有三分之一（加盟）表，这使得许多一对多作者与书之间的关系（一个作者可以写很多书和一本书，可以从许多作者写的）。
I'll try to create the two tables 'Author' and 'Book'. In SQL, there should be a third (join) table, which makes the many-to-many relation between Author and Book (one author could have written many books and a book could be written from many authors).
这是我到目前为止有：
namespace CodeFirst.Models.Web
{
public class Author
{
public Author()
{
this.Books = new HashSet<Book>();
}
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[Key]
public int ID { get; set; }
[Required]
public string Name { get; set; }
public ICollection<Book> Books { get; set; }
}
public class Book
{
public Book()
{
this.Authors = new HashSet<Author>();
}
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[Key]
public int ID { get; set; }
[Required]
public string Name { get; set; }
public ICollection<Author> Authors { get; set; }
}
// Should I do something like that:
public class AuthorMapping : EntityTypeConfiguration<Author>
{
public AuthorMapping() : base()
{
//this.HasMany (g => g.Books)
// .WithMany(m => m.Authors)
// .Map (gm => gm.ToTable ("Author_Book")
// .MapLeftKey ("AuthorID")
// .MapRightKey("BookID"));
}
}
public class CodeFirstModelContext : DbContext
{
public CodeFirstModelContext() : base()
{
this.Database.Connection.ConnectionString = @".\MSSQLSERVER2008;Database=CodeFirst;Trusted_Connection=true;";
}
public DbSet<Author> Authors { get; set; }
public DbSet<Book> Books { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Configurations.Add(new AuthorMapping());
// tell Code First to ignore PluralizingTableName convention
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
}
}
[EnableClientAccess()]
public class CodeFirstDomainService : DomainService
{
public CodeFirstDomainService()
{
this.m_modelContext = new CodeFirstModelContext();
}
public IQueryable<Author> GetAuthors()
{
return this.m_modelContext.Authors;//.Include("Books");
}
public void InsertAuthor(Author Author)
{
this.m_modelContext.Insert(Author);
}
public void UpdateAuthor(Author Author)
{
this.m_modelContext.Update(Author, this.ChangeSet.GetOriginal(Author));
}
public void DeleteAuthor(Author Author)
{
this.m_modelContext.Delete(Author);
}
public IQueryable<Book> GetBooks()
{
return this.m_modelContext.Books;//.Include("Authors");
}
public void InsertBook(Book Author)
{
this.m_modelContext.Insert(Author);
}
public void UpdateBook(Book Author)
{
this.m_modelContext.Update(Author, this.ChangeSet.GetOriginal(Author));
}
public void DeleteBook(Book Author)
{
this.m_modelContext.Delete(Author);
}
protected override void Dispose(bool disposing)
{
if (disposing)
this.m_modelContext.Dispose();
base.Dispose(disposing);
}
protected override bool PersistChangeSet()
{
this.m_modelContext.SaveChanges();
return base.PersistChangeSet();
}
private CodeFirstModelContext m_modelContext;
}
}
最明显的问题是，导航性能（在作者与书作者）图书不会从我的客户端项目中的代码设计器创建。
The most obvious problem is, that the navigation properties (Books in Author and Authors in Book) aren't created from the code designer in my client project.
什么我需要做什么？
编辑：
好吧，现在我能够只NavigationProperties之一同时使用。如果我尝试'包含'两个我得到了以下错误：
Okay, now I'm able to use only one of the NavigationProperties simultaneously. If I try to 'Include' both I'm getting the following error:
Association 'Author_Book' defined on entity type 'CodeFirst.Models.Web.Author' is invalid. It is a foreign key association but the property type is not a singleton.
这是我更新的代码：
public class Author
{
public Author()
{
this.Books = new Collection<Book>();
}
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[Key]
public int ID { get; set; }
[MaxLength(32)]
[Required]
public string Name { get; set; }
[Association("Author_Book", "ID", "ID")]
[Include]
public Collection<Book> Books { get; set; }
}
public class Book
{
public Book()
{
this.Authors = new Collection<Author>();
}
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[Key]
public int ID { get; set; }
[MaxLength(32)]
[Required]
public string Name { get; set; }
[Association("Author_Book", "ID", "ID")]
[Include]
public Collection<Author> Authors { get; set; }
}
public class AuthorMapping : EntityTypeConfiguration<Author>
{
public AuthorMapping() : base()
{
this.HasMany (g => g.Books)
.WithMany(m => m.Authors)
.Map (gm => gm.ToTable("Author_Book"));
}
}
public class BookMapping : EntityTypeConfiguration<Book>
{
public BookMapping() : base()
{
this.HasMany (m => m.Authors)
.WithMany(g => g.Books)
.Map (gm => gm.ToTable("Author_Book"));
}
}
在我看来，那实体框架仍然ISN ŧ能够处理许多一对多的关系。 。至少，这是错误信息意味着什么
It seems to me, that Entity Framework still isn't able to deal with many-to-many relations. At least, that's what the error message implies.
EDIT2：
我已经改变了我的代码我读过之后< A HREF =http://social.msdn.microsoft.com/Forums/en/adodotnetentityframework/thread/d894c8af-5985-4995-88e2-c8733e4a51ea相对=nofollow>这个职位上social.msdn
public class Author
{
public Author()
{
this.Books = new Collection<Book>();
}
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[Key]
public int ID { get; set; }
[MaxLength(32)]
[Required]
public string Name { get; set; }
[Association("Author_Book", "Book_ID", "Author_ID")]
[Include]
[ForeignKey("Book_ID")]
public Collection<Book> Books { get; set; }
public int Book_ID { get; set; }
}
public class Book
{
public Book()
{
this.Authors = new Collection<Author>();
}
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[Key]
public int ID { get; set; }
[MaxLength(32)]
[Required]
public string Name { get; set; }
[Association("Author_Book", "Author_ID", "Book_ID")]
[Include]
[ForeignKey("Author_ID")]
public Collection<Author> Authors { get; set; }
public int Author_ID { get; set; }
}
它不会固定我的问题。相同的误差仍然存在。我测试过去除AssociationAttribute没有成功。我做somethinf错在这里？
It doesn't fixed my problem. The same error is still present. I've tested to remove the AssociationAttribute without success. Am I doing somethinf wrong here?
推荐答案
我觉得这里的问题在于WCF RIA服务，没有什么EF相关。也就是说，WCF不喜欢的接口。解决办法是使用收藏而不是的ICollection 的。我敢肯定，EF不会介意它，它会解决您的WCF问题。
I think problem here lies in the WCF RIA service, not anything EF related. That is, that WCF doesn't like interfaces. Solution would be use Collection instead of ICollection. I'm sure EF won't mind it and it will fix your WCF problem.
修改：这可能会解决你的问题的 http://social.msdn.microsoft.com/Forums/en/adodotnetentityframework/thread/d894c8af-5985-4995-88e2-c8733e4a51ea
Edit: This may solve your problem http://social.msdn.microsoft.com/Forums/en/adodotnetentityframework/thread/d894c8af-5985-4995-88e2-c8733e4a51ea
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