entity-framework - .net core Entity Framework 两种关系可以使用相同的外键

Question

我有一些继承自基本模型的模型:

public class Filter
{
    public int Id { get; set; }
    public int FeedId { get; set; }
    public FilterOperator FilterOperator { get; set; }
    [Required, MaxLength(100)] public string Name { get; set; }
    [Required, MaxLength(100)] public string Expression { get; set; }
    [Required, MaxLength(100)] public string FieldName { get; set; }
}

然后我有另一个模型:

public class Conversion : Filter
{
    public MathOperator MathOperator { get; set; }
    public double Value { get; set; }
}

这些都与名为 Feed 的实体具有类似的关系:

public class Feed
{
    public int Id { get; set; }
    [Required, MaxLength(100)] public string CategoryId { get; set; }
    [Required, MaxLength(2083)] public string Url { get; set; }
    public FeedType Type { get; set; }
    public bool Active { get; set; }

    public Category Category { get; set; }
    public ICollection<Conversion> Conversions { get; set; }
    public ICollection<FieldMap> FieldMaps { get; set; }
    public ICollection<Filter> Filters { get; set; }
    public ICollection<Rule> Rules { get; set; }
    public ICollection<Transformation> Transformations { get; set; }
}

当我尝试运行 add-migration 命令时，出现此错误:

Both relationships between 'Conversion' and 'Feed.Conversions' and between 'Filter' and 'Feed.Filters' could use {'FeedId'} as the foreign key. To resolve this configure the foreign key properties explicitly on at least one of the relationships.

所以在我的DbContext中我添加了这些行:

modelBuilder.Entity<Feed>().HasMany(m => m.Conversions).WithOne().HasForeignKey(m => m.FeedId);
modelBuilder.Entity<Feed>().HasMany(m => m.Filters).WithOne().HasForeignKey(m => m.FeedId);
modelBuilder.Entity<Feed>().HasMany(m => m.Rules).WithOne().HasForeignKey(m => m.FeedId);
modelBuilder.Entity<Feed>().HasMany(m => m.Transformations).WithOne().HasForeignKey(m => m.FeedId);

但我仍然遇到同样的问题。 有谁知道我可以做些什么来解决这个问题？

Answer 1

您需要移动 public ICollection<Conversion> Conversions { get; set; }以避免错误。

自从您使用 TPH它将使用单个表来存储层次结构中所有类型的数据。鉴别器列用于识别每行代表哪种类型。

然后您可以使用以下方法获取派生实体:

public class SampleContext : DbContext
{
    public DbSet<Filter> Contracts { get; set; }
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Conversion>().HasBaseType<Filter>();

    }
}

Controller :

var conversions = _context.Filters.OfType<Conversion>().ToList();

引用https://www.learnentityframeworkcore.com/inheritance/table-per-hierarchy#convention