EF4.1 代码第一个一对多自引用

Question

我正在尝试首先使用 EF4.1 代码进行一对多自引用。我的实体看起来像这样

public class Site
{
    public int Id { get; set; }
    public int? ParentId { get; set; }
    public string Sitename { get; set; }

    public virtual Site ChildSite { get; set; }
    public virtual ICollection<Site> ChildSites { get; set; }
}

在我的上下文类中，我这样做是为了进行自我引用

modelBuilder.Entity<Site>()
    .HasOptional(s => s.ChildSite)
    .WithMany(s => s.ChildSites)
    .HasForeignKey(s => s.ParentId);

但是当我尝试使用此代码向我的数据库添加一些虚拟数据时

var sites = new List<Site>
{
    new Site { ParentId = 0, Sitename = "Top 1" },
    new Site { ParentId = 0, Sitename = "Top 2" },
    new Site { ParentId = 0, Sitename = "Top 3" },
    new Site { ParentId = 0, Sitename = "Top 4" },
    new Site { ParentId = 1, Sitename = "Sub 1_5" },
    new Site { ParentId = 1, Sitename = "Sub 1_6" },
    new Site { ParentId = 1, Sitename = "Sub 1_7" },
    new Site { ParentId = 1, Sitename = "Sub 1_8" },
    new Site { ParentId = 2, Sitename = "Sub 2_9" },
    new Site { ParentId = 2, Sitename = "Sub 2_10" },
    new Site { ParentId = 2, Sitename = "Sub 2_11" },
    new Site { ParentId = 2, Sitename = "Sub 2_12" },
    new Site { ParentId = 3, Sitename = "Sub 3_13" },
    new Site { ParentId = 3, Sitename = "Sub 3_14" },
    new Site { ParentId = 3, Sitename = "Sub 3_15" },
    new Site { ParentId = 3, Sitename = "Sub 3_16" },
    new Site { ParentId = 4, Sitename = "Sub 4_17" },
    new Site { ParentId = 4, Sitename = "Sub 4_18" },
    new Site { ParentId = 4, Sitename = "Sub 4_19" },
    new Site { ParentId = 4, Sitename = "Sub 4_20" }
};
sites.ForEach(s => context.Sites.Add(s));
context.SaveChanges();

我得到这个错误：

无法确定主端 'Cms.Model.Site_ChildSite' 关系。多个添加的实体可能 具有相同的主键。

我在这里错过了什么？

编辑：

这是我的问题的解决方案。我从实体中删除了public virtual Site ChildSite { get; set; }

public class Site
{
    public int Id { get; set; }
    public int? ParentId { get; set; }
    public string Sitename { get; set; }

    public virtual ICollection<Site> ChildSites { get; set; }
}

然后我把 modelBuilder 改成了这个

modelBuilder.Entity<Site>()
    .HasMany(s => s.ChildSites)
    .WithOptional()
    .HasForeignKey(s => s.ParentId);

由于数据库的自动生成似乎不起作用，我继续像这样自己创建了表

int Id, not null, primary key
int ParentId, null
string Sitename, null

一切都如我所愿。

第二次编辑

以及让虚拟数据的自动生成工作的最后一步

var parent1 = new Site
{
    Sitename = "Top 1",
    ChildSites = new List<Site>
        {
            new Site {Sitename = "Sub 1_5"},
            new Site {Sitename = "Sub 1_6"},
            new Site {Sitename = "Sub 1_7"},
            new Site {Sitename = "Sub 1_8"}
        }
};

ect . . . 

context.Sites.Add(parent1);
context.SaveChanges();

请参阅下面的 Slauma 答案

Answer 1

我有一个不同的模型，但我会发布我的情况所需的内容，它适用于 MVC 3 上的 EF4.1：

型号

public class Page
{
    public int Id { get; set; }
    public virtual string Title { get; set; }

    public int? ParentId { get; set; }
    public virtual Page Parent { get; set; }
    public virtual ICollection<Page> Children { get; set; }
}

数据库（使用流畅的 API）

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
     modelBuilder.Entity<Page>()
                 .HasOptional(s => s.Parent)
                 .WithMany(s => s.Children)
                 .HasForeignKey(s => s.ParentId);
}

初始化器

var page1 = new Page()
{
     Title = "title"
};

context.Pages.Add(page1);

var page2 = new Page()
{
      Parent = page1,
      Title = "title2",
};

context.Pages.Add(page2);

Answer 2

您的映射是正确的，您不需要删除ChildSite 属性。创建实体时不能使用外键属性，并“猜测”这些自动生成的数字在存储实体后将如何，并在存储的同一实体中使用这些数字。

以下应该可以工作并在数据库中创建预期的行：

var parent1 = new Site
{
    Sitename = "Top 1",
    ChildSites = new List<Site>
        {
            new Site {Sitename = "Sub 1_5"},
            new Site {Sitename = "Sub 1_6"},
            new Site {Sitename = "Sub 1_7"},
            new Site {Sitename = "Sub 1_8"}
        }
};
var parent2 = new Site
{
    Sitename = "Top 2",
    ChildSites = new List<Site>
        {
            new Site {Sitename = "Sub 2_9"},
            new Site {Sitename = "Sub 2_10"},
            new Site {Sitename = "Sub 2_11"},
            new Site {Sitename = "Sub 2_12"}
        }
};
var parent3 = new Site
{
    Sitename = "Top 3",
    ChildSites = new List<Site>
        {
            new Site {Sitename = "Sub 3_13"},
            new Site {Sitename = "Sub 3_14"},
            new Site {Sitename = "Sub 3_15"},
            new Site {Sitename = "Sub 3_16"}
        }
};
var parent4 = new Site
{
    Sitename = "Top 4",
    ChildSites = new List<Site>
        {
            new Site {Sitename = "Sub 4_17"},
            new Site {Sitename = "Sub 4_18"},
            new Site {Sitename = "Sub 4_19"},
            new Site {Sitename = "Sub 4_20"}
        }
};
context.Sites.Add(parent1);
context.Sites.Add(parent2);
context.Sites.Add(parent3);
context.Sites.Add(parent4);
context.SaveChanges();

编辑

如果数据库中存在外键表示的实体，您可以使用它 - 例如：

var site = context.Sites.Single(s => s.Sitename == "Top 1");
site.ParentId = 4; // set a parent for "Top 1"
context.SaveChanges();

添加一个新的孩子：

var site = context.Sites.Single(s => s.Sitename == "Top 1");
site.ChildSites.Add(new Site { Sitename = "Sub 1_9" });
context.SaveChanges();

移除一个孩子：

var site = context.Sites.Single(s => s.Sitename == "Top 1");
// works because of lazy loading
var childToRemove = site.ChildSites.Single(s => s.Sitename == "Sub 1_9");
site.ChildSites.Remove(childToRemove);
context.SaveChanges();

等等

Answer 3

首先 - 不要指定 id - 我认为数据库负责为您的实体添加自动编号。

尝试以这种方式填充您的数据库：

var top1 = new Site { Sitename = "Top 1" };
var sub15 = new Site { ChildSite = top1 , Sitename = "Sub 1_5" };
var sub16 = new Site { ChildSite = top1 , Sitename = "Sub 1_6" };
var sub17 = new Site { ChildSite = top1 , Sitename = "Sub 1_7" };
...
context.Sites.Add(top1);

var top2 = new Site { Sitename = "Top 2" };
var sub29 = new Site { ChildSite = top2 , Sitename = "Sub 2_9" };
var sub210 = new Site { ChildSite = top2 , Sitename = "Sub 2_10" };
var sub211 = new Site { ChildSite = top2 , Sitename = "Sub 2_11" };
....
context.Sites.Add(top2);

....
context.SaveChanges();

下一步：我认为您应该将 ChildSite 称为 ParentSite，这将使代码更易于阅读：

var top1 = new Site { Sitename = "Top 1" };
var sub15 = new Site { ParentSite = top1 , Sitename = "Sub 1_5" };
var sub16 = new Site { ParentSite = top1 , Sitename = "Sub 1_6" };
var sub17 = new Site { ParentSite = top1 , Sitename = "Sub 1_7" };
...
context.Sites.Add(top1);

var top2 = new Site { Sitename = "Top 2" };
var sub29 = new Site { ParentSite = top2 , Sitename = "Sub 2_9" };
var sub210 = new Site { ParentSite = top2 , Sitename = "Sub 2_10" };
var sub211 = new Site { ParentSite = top2 , Sitename = "Sub 2_11" };
....
context.Sites.Add(top2);

....
context.SaveChanges();

Answer 4

不知道为网站保留一组ChildSite 和一个ChildSites 的目的是什么。试试这个配置。

public class Site
{
    public int Id { get; set; }
    public int? ParentId { get; set; }
     public virtual  Site Parent { get; set; }
    public string Sitename { get; set; }

    public virtual ICollection<Site> ChildSites { get; set; }
}

modelBuilder.Entity<Site>()
    .HasOptional(s => s.Parent)
    .WithMany(s => s.ChildSites)
    .HasForeignKey(s => s.ParentId);

编辑 当您插入时，您需要这样做。

 site s1=   new Site { ParentId = 0, Sitename = "Top 1" };
 site s2=   new Site { ParentId = 0, Sitename = "Top 2" };
 site s3=   new Site { ParentId = 0, Sitename = "Top 3" };
//....
 site s4=  new Site { Parent = s1, Sitename = "Sub 1_5"};