我有两个实体类,Contact
和 User
。
User
ContactID
是Contact
的外键。我可以显示User
与Contact
的关系.
现在我还需要Contact
User
表中与相同外键的关系User
(不是Contact
public class Contact{
public int ContactID {get;set;}
// This relation doesn't work
// Need to Make this Work
public User ContactUser {get;set;}
}
public class User {
public string Id {get;set;}
public int? ContactID {get;set;}
// This Relation works
[ForeignKey("ContactID")]
public Contact Contact {get;set;}
}
所以我需要使ContactUser
关系在Contact
上工作.我应该使用哪种映射?
编辑
正如建议的那样,我使用了: modelBuilder.Entity<Contact>().HasRequired(c => c.ContactUser).WithOptional(pi => pi.Contact);
我从User
中删除了ForeignKey
属性,它会导致Multiplicity...error
但是我得到错误,例如:Invalid column name 'User_Id'.
您要查找的是一个
一对一映射
在StackOverflow上有一个很棒的anwser。
在您的情况下,显式是必需的:
-
modelBuilder 需要 WithOptional-Methode
.WithOptional(pi => pi.Contact);
-
没有
ContactID
属性
EF 6.0 的示例
public class Contact
{
[Key]
public int ContactId { get; set; }
public string ContactName { get; set; }
public User ContactUser { get; set; }
}
public class User
{
[Key]
public int UserId { get; set; }
public string UserName { get; set; }
public Contact Contact { get; set; }
}
在 DbContext-class 中:
public class CodeFirstContext : DbContext
{
public CodeFirstContext()
{
Database.SetInitializer(new DropCreateDatabaseIfModelChanges<CodeFirstContext>());
}
public DbSet<Contact> Contacts { get; set; }
public DbSet<User> Users { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<User>()
.HasRequired(co => co.Contact)
.WithOptional(cu => cu.ContactUser);
base.OnModelCreating(modelBuilder);
}
}
在这种情况下,现在说用户的联系人属性是可选的,联系人的用户属性是必需的。我希望这是适合您项目的星座。
控制台测试
class Program
{
static void Main(string[] args)
{
using (var db = new CodeFirstContext())
{
Console.Write("Enter a name: ");
var name = Console.ReadLine();
var cont = new Contact { ContactName = name };
db.Contacts.Add(cont);
db.SaveChanges();
var usr = new User { UserName = "MyUsername", Contact = cont };
db.Users.Add(usr);
db.SaveChanges();
var query = from b in db.Contacts
orderby b.ContactName
select b;
Console.WriteLine("All contacts in the database:");
foreach (var item in query)
{
Console.WriteLine(item.ContactName);
}
Console.WriteLine("Press any key to exit...");
Console.ReadKey();
}
}
}
试试这个:
public class Contact
{
[Key, DatabaseGenerated(DatabaseGeneratedOption.None)]
public int ContactId { get; set; }
public string ContactName { get; set; }
[ForeignKey("ContactId")]
public User ContactUser { get; set; }
}