[英]EF Code First Foreign Key Relationship
我有以下情況:
我的模型類如下所示:
public class GameTable
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid Id
{
get;
set;
}
[Required]
public string Name { get; set; }
[Required]
public string Description { get; set; }
public Guid CreatorId { get; set; }
[ForeignKey(nameof(CreatorId))]
public Account Creator { get; set; }
}
public class Account
{
public Account()
{
Elo = 1000;
}
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid Id { get; set; }
[Required]
[MaxLength(15)]
[MinLength(4)]
public string Name { get; set; }
[Required]
[MaxLength(32)]
[MinLength(32)]
public string PasswordHash { get; set; }
public int Elo { get; set; }
public bool IsAdmin { get; set; }
public Guid? CurrentTableId { get; set; }
[ForeignKey(nameof(CurrentTableId))]
public virtual GameTable CurrentTable { get; set; }
}
我的上下文當前看起來像這樣:
[Export(typeof(MyDbContext)), PartCreationPolicy(CreationPolicy.Shared)]
[DbConfigurationType(typeof(MySqlEFConfiguration))]
public class MyDbContext : DbContext
{
public MyDbContext() : base("DbContextCon")
{
Database.SetInitializer<PiksenDbContext>(new CreateDatabaseIfNotExists<PiksenDbContext>());
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
}
public virtual DbSet<Account> Accounts { get; set; }
public virtual DbSet<SecurityToken> SecurityTokens { get; set; }
public virtual DbSet<GameTable> GameTables { get; set; }
}
不幸的是,這不適用於像這樣設置的兩個外鍵。 以下消息目前讓我有些頭疼:
System.InvalidOperationException:'無法確定類型'namespace.GameTable'和'namespace.Account'之間的關聯的主要終點。 必須使用關系流利的API或數據注釋顯式配置此關聯的主要端。
但是,當我注釋掉FK關系之一時,一切都很好。 似乎這兩者之間存在某種沖突。
我想獲得的結果是一個可空FK在Account
名為CurrentTableId
和非空的FK GameTable
所謂CreatorId
。
在FK關系的每一側,您都可以(通常應該)具有導航屬性。 並且當存在多個FK關系時,可以使用InversePropertyAttribute指定一對導航屬性代表哪個FK。
例如
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ef62test
{
class Program
{
public class GameTable
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid Id
{
get;
set;
}
[Required]
public string Name { get; set; }
[Required]
public string Description { get; set; }
public Guid CreatorId { get; set; }
[ForeignKey(nameof(CreatorId))]
public Account Creator { get; set; }
[InverseProperty(nameof(Account.CurrentTable))]
public ICollection<Account> CurrentPlayers { get; } = new HashSet<Account>();
}
public class Account
{
public Account()
{
Elo = 1000;
}
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid Id { get; set; }
[Required]
[MaxLength(15)]
[MinLength(4)]
public string Name { get; set; }
[Required]
[MaxLength(32)]
[MinLength(32)]
public string PasswordHash { get; set; }
public int Elo { get; set; }
public bool IsAdmin { get; set; }
public Guid? CurrentTableId { get; set; }
[ForeignKey(nameof(CurrentTableId))]
public virtual GameTable CurrentTable { get; set; }
[InverseProperty(nameof(GameTable.Creator))]
public ICollection<GameTable> CreatedTables { get; } = new HashSet<GameTable>();
}
public class MyDbContext : DbContext
{
public MyDbContext() : base("DbContextCon")
{
Database.SetInitializer<MyDbContext>(new CreateDatabaseIfNotExists<MyDbContext>());
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
}
public virtual DbSet<Account> Accounts { get; set; }
//public virtual DbSet<SecurityToken> SecurityTokens { get; set; }
public virtual DbSet<GameTable> GameTables { get; set; }
}
static void Main(string[] args)
{
Database.SetInitializer(new DropCreateDatabaseAlways<MyDbContext>());
using (var db = new MyDbContext())
{
db.Database.CreateIfNotExists();
}
Console.WriteLine("Hit any key to exit.");
Console.ReadKey();
}
}
}
它暗示您要創建一個自參考GameTable表。 為此,您需要向帳戶表中添加一個Collection屬性,例如。
public virtual ICollection<GameTable> Children { get; set; }
整個代碼塊看起來像
public class GameTable
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid Id
{
get;
set;
}
[Required]
public string Name { get; set; }
[Required]
public string Description { get; set; }
public Guid CreatorId { get; set; }
[ForeignKey(nameof(CreatorId))]
public Account Creator { get; set; }
}
public class Account
{
public Account()
{
Elo = 1000;
}
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid Id { get; set; }
[Required]
[MaxLength(15)]
[MinLength(4)]
public string Name { get; set; }
[Required]
[MaxLength(32)]
[MinLength(32)]
public string PasswordHash { get; set; }
public int Elo { get; set; }
public bool IsAdmin { get; set; }
public Guid? CurrentTableId { get; set; }
[ForeignKey(nameof(CurrentTableId))]
public virtual GameTable CurrentTable { get; set; }
public virtual ICollection<GameTable> Children { get; set; }
}
希望它能解決您的問題。
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