实体框架过滤的导航属性 [英] Entity Framework Filtered Navigation Properties

问题描述

有没有办法使用EF6 /代码首先设置导航属性的过滤器？我想要实现类似于下面的内容，其中Farm.Pigs返回类型等于pig的动物的集合（但不将数据库首先从数据库中加载，而不是将它们存储在单独的表中）。这是可能吗？

  public class Farm {
 public int Id {get;组; } 
 
 public virtual ICollection< Animal>猪{get;组; } 
 
 public virtual ICollection< Animal>奶牛{get;组; } 
} 
 
 public class Animal {
 public int Id {get;组; } 
 
 public int FarmId？ {get;组; } 
 
 public virtual Farm Farm {get;组; } 
 
 public string Name {get;组; } 
} 
 
 public enum AnimalType {
 Pig，Cow 
} 
  

更新

将更新移动到一个新问题：实体框架一个多TPH映射

解决方案

你不能按照您的要求执行此操作，它是实体框架的当前限制。

如果创建了继承关系，您可以以不同的方式实现，例如

  public class Animal {
 public int Id {get;组; } 
 
 public AnimalType Type {get;组; } 
 
 public string Name {get;组; } 
} 
 
 public class Pig：Animal {...} 
 
 public class Cow：Animal {...} 
  

然后，您可以按照以下文章配置Table per Hierarchy（TPH）：

http://weblogs.asp.net/manavi/archive/2010/12/24/inheritance-mapping-strategies-with-entity-framework-code-first -ctp5-part-1-table-per-hierarchy-tph.aspx

Is there a way to set a filter on a navigation property using EF6/code first?

I want to achieve something similar to the below, where Farm.Pigs returns a collection of animals whose type is equal to pig (but without loading the whole collection from the database first - and not storing them in a separate table). Is this possible?

public class Farm {
    public int Id { get; set; }

    public virtual ICollection<Animal> Pigs { get; set; }

    public virtual ICollection<Animal> Cows { get; set; }
}

public class Animal {
    public int Id { get; set; }

    public int FarmId? { get; set; }

    public virtual Farm Farm { get; set; }

    public string Name { get; set; }
}

public enum AnimalType {
    Pig, Cow
}

Update

Moved the update to a new question: Entity Framework One-Many TPH Mapping

解决方案

You can't do this in the way you asked, it is a current limitation of entity framework.

You could achieve it a different way if you created an inheritance relationship, i.e.

public class Animal {
    public int Id { get; set; }

    public AnimalType Type { get; set; }

    public string Name { get; set; }
}

public class Pig : Animal { ... }

public class Cow : Animal { ... }

You could then configure Table per Hierarchy (TPH) as in the following article:

http://weblogs.asp.net/manavi/archive/2010/12/24/inheritance-mapping-strategies-with-entity-framework-code-first-ctp5-part-1-table-per-hierarchy-tph.aspx

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