[英]Parent/Child with EF6 child collection always null
每當我通過EF拉MyList對象時,父對象就正確關聯了,而Children集合始終為null。 不知道我在做什么錯,幾乎每篇文章都表明這樣做。
數據庫
CREATE TABLE [dbo].[MyList] (
[MyListId] BIGINT IDENTITY (1, 1) NOT NULL,
[ParentMyListId] BIGINT NULL,
CONSTRAINT [PK_MyList] PRIMARY KEY CLUSTERED ([MyListId] ASC) WITH (FILLFACTOR = 90),
CONSTRAINT [FK_MyList_MyList_MyListId] FOREIGN KEY (ParentMyListId) REFERENCES MyList(MyListId)
);
模型
public class MyList
{
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public long MyListId { get; set; }
public long? ParentMyListId { get; set; }
[ForeignKey("ParentMyListId")]
public virtual List MyListParent { get; set; }
public virtual ICollection<MyList> MyListChildren { get; set; }
}
數據庫上下文
public class MyContext : DbContext
{
public MyContext() : base(Properties.Settings.Default.DbContext)
{
Configuration.LazyLoadingEnabled = false;
}
public DbSet<MyList> MyLists { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<MyList>()
.ToTable("MyList", "dbo")
.HasOptional(x => x.MyListParent)
.WithMany(x => x.MyListChildren)
.HasForeignKey(x => x.ParentMyListId)
.WillCascadeOnDelete(false);
}
base.OnModelCreating(modelBuilder);
}
我在EF 6.1.3版本中嘗試了相同的結構,它的工作原理很吸引人。 我添加了輸出圖像和db中存在的數據。 如果禁用配置中的加載,唯一可能會停止工作的事情。 希望它對您有用,請嘗試我的示例代碼。
// Your entity class I added name property to show you the results
public class MyList
{
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public long MyListId { get; set; }
public long? ParentMyListId { get; set; }
public string Name { get; set; }
[ForeignKey("ParentMyListId")]
public virtual MyList MyListParent { get; set; }
public virtual ICollection<MyList> MyListChildren { get; set; }
}
// DBContext please note no configuration properties set just default constructor
// you need t check here if you have set soemthing here
public class TestContext : DbContext
{
public TestContext()
: base("name=TestConnection")
{
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<MyList>()
.ToTable("MyList", "dbo")
.HasOptional(x => x.MyListParent)
.WithMany(x => x.MyListChildren)
.HasForeignKey(x => x.ParentMyListId)
.WillCascadeOnDelete(false);
}
public virtual DbSet<MyList> Lists { get; set; }
}
控制台應用程序顯示結果:
static void Main(string[] args)
{
using (var ctx = new TestContext())
{
// for testing to see al working
//this is important to read the entity first .
var parent = ctx.Lists.ToList();
foreach (var p in parent)
{
foreach (var child in p.MyListChildren)
{
Console.WriteLine(string.Format(@"Parent Name {0} has child with name {1}", p.Name, child.Name));
}
}
}
Console.ReadLine();
}
在數據庫中輸出應用程序和數據...
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