Csharp 如何定义EFCore中的多个穿透

发布于03月12日

假定有以下实体:

public class User
{
    public int Id;
    public List<Team> Teams { get; set; } // how to setup this in EFCore?
}

public class Team
{
    public int Id;
    public List<Member> Members { get; set; }
}

// Pivot
public class Member
{
    public int Id;
    public string Role;

    public User User { get; set; }
    public Team Team { get; set; }
}

我如何在EFCore配置中定义User到Member有许多Team？

我知道我可以创建一个派生自Member的属性，但我想知道是否可以在EFCore中定义它.

public class User
{
    public int Id;
    public List<Member> Members { get; set; }
    public List<Team> Teams => Members.Select(m => m.Team).ToList();
}

类似于拉威尔(https://laravel.com/docs/10.x/eloquent-relationships#has-many-through)

推荐答案

首先，将您的字段转换为属性:

public class User
{
    public int Id { get; set; }
    // ...
}

public class Team
{
    public int Id { get; set; }
    // ...
}

public class Member
{
    public int Id { get; set; }
    // ...
}

然后，如果您不想更改导航属性，您可以在OnModelCreating中使用fluent API进行设置:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<User>()
        .HasMany(u => u.Teams)
        .WithMany()
        .UsingEntity<Member>();
}

另请查看EF Core: Many-to-many relationships的文档，有不同的选项来设置此 struct ，包括完全限定的关系，这些关系不需要显式流畅的API配置(但在编写查询时可能需要一些逻辑).