流利的nHibernate - 用组合键映射儿童产生空引用 [英] Fluent nHibernate - Mapping Children with Composite Keys Yielding Null References

问题描述

给定一个简单的父 - >孩子（CK，CK）这样的设置..我有麻烦添加一个新的子对象，它得到父引用。所以我会以这种方式添加对象..

$ $ p $ $ $ $ $ $ $ $变种父母=新父母{
Children = new List< ; Child> {
new Child {
Other = otherReference
}
}
};

甚至使用 Add（）方法...

lockquote

parent.Children.Add（new Child {Other = other}）;

对父的引用不会被传入。它只是作为一个空属性结束。

{不能将值NULL插入到'ParentId'列'mssql_test.Children'列中}

I can 这个...

$ p $ new Child {
Parent = parentReference，
Other = otherReference
}


但这似乎有点多余。我的理解是，它应该能够自己推断参考。如果这是不可能的，也许我只是误解。谁能帮我？

类

  class父母{
 int Id {get;组; } 
 IList< Child>孩子{get;组; } 
} 
 class其他{
 int Id {get;组; } 
} 
 class Child {
父Parent {get;组; } 
其他其他{get;组; } 
 //其他属性
} 
  

映射

  ChildMap（）{
 CompositeId（）
 .KeyReference（x => x.Parent，ParentId）
 .KeyReference（x => x.Other，OtherId）; 
 
 
 ParentMap（）{
 HasManyToMany（x => x.Children）
 .AsBag（）
 .ChildKeyColumns.Add（new [ ] {ParentId，OtherId}）
 .Inverse（）
 .Cascade.All（））
 .Table（[Test]）; 
 
 $ / code $ / $ p 
 
解决方案
 

问题是，您应该将HasMany映射为HasManyToMany的子集合。这是映射应该看起来如何：


$ Child $（$）
CompositeId（）//这是很好的$ b $ .KeyReference（x => x.Parent，ParentId）
.KeyReference（x => x.Other，OtherId）;


ParentMap（）{//这是修正
HasMany（c => c.Children）
.Inverse（）
。 Cascade.All（）
.KeyColumn（ParentId）//如果父Id标示映射到ParentId不需要col
.Table（[Test]）;
}


Given a simple parent -> child (CK,CK) setup like this .. I am having trouble with adding a new child object and it getting the parent reference. So I would add the object in such a way ..

var parent = new Parent{
  Children = new List<Child>{
   new Child{
     Other = otherReference
   }
  }
};

Or even adding it using the Add() method...

parent.Children.Add(new Child { Other = other });

The reference to the Parent does not get pushed through. It just ends up as a null property. I get the following exception.

{"Cannot insert the value NULL into column 'ParentId', table 'mssql_test.Children'; column does not allow nulls. INSERT fails.\r\nThe statement has been terminated."}

I can do this ...

new Child { 
   Parent = parentReference,
   Other = otherReference
}

But that seems a bit redundant. My understanding is that it should be able to infer the reference by itself. If this is not possible, perhaps I am just misunderstanding. Can anyone help me? I have an outline of my code below.

Classes

class Parent {
  int Id { get; set; }
  IList<Child> Children { get; set; }
}
class Other {
  int Id { get; set; }
}
class Child {
  Parent Parent { get; set; }
  Other Other { get; set; }
  // other properties
}

Mapping

 ChildMap() {
      CompositeId()
        .KeyReference(x => x.Parent, "ParentId")
        .KeyReference(x => x.Other, "OtherId");
    }

    ParentMap(){
     HasManyToMany(x => x.Children)
                    .AsBag()
                    .ChildKeyColumns.Add(new[] { "ParentId", "OtherId" })
                    .Inverse()
                    .Cascade.All())
                    .Table("[Test]");
}

解决方案

As @KeithS points out the problem is that you have mapped the Child collection as HasManyToMany when it should be HasMany. Here is how the mapping should look:

  ChildMap() {
      CompositeId() //This is is good
        .KeyReference(x => x.Parent, "ParentId")
        .KeyReference(x => x.Other, "OtherId");
  }

  ParentMap(){ //This is the fix
        HasMany(c => c.Children)
          .Inverse()
          .Cascade.All()
          .KeyColumn("ParentId") //Not needed if Parent Id prop maps to ParentId col
          .Table("[Test]");
  }

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