Question

我一直在寻找尝试在EF中创建并行的一对多关系。这是我的意思：

我有两个课程，交易和用户：

public class Transaction
{
    public int ID { get; set; }

    public string ExecutorID { get; set; }
    public virtual User Executor { get; set; }

    public string ConsumerID { get; set; }
    public virtual User Consumer { get; set; }
}

public class User
{
    public UserRole Role { get; set; }
    public string Name { get; set; }

    public string Id { get; set; }
    public string Pin { get; set; }

    public virtual List<Transaction> ExecutedTransactions { get; set; }
    public virtual List<Transaction> Transactions { get; set; } 
}

如果您还没有看到它，我在对象Transactions和Executed Transactions之间有两个链接。我的问题是如何告诉EF区分这两者？

交易应指向所有Transaction其中User.ID == Transaction.ConsumerID和ExecutedTransactions所在的User.ID == Transaction.ExecutorID

Answer 1

以下是从Food派生Book和Item的类。

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<Food> Foods { get; set; }
    public ICollection<Book> Books { get; set; }
}
public abstract class Item
{
    public int Id { get; set; }
    public string Name { get; set; }
}
public class Food : Item
{
    public int CookedById { get; set; }
    [ForeignKey("CookedById")]
    public Person CookedBy { get; set; }
}
public class Book : Item
{
    public int AuthorId { get; set; }
    [ForeignKey("AuthorId")]
    public Person Author { get; set; }
}

选项每个层次结构的表

public class AppContext : DbContext
{
    public DbSet<Person> People { get; set; }
    public DbSet<Item> Items { get; set; }
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Person>().HasMany(p => p.Foods).WithRequired(f => f.CookedBy).WillCascadeOnDelete(false);
    }
}

结果将是 2个表格，表格Person和Item自动Discriminator列，其中将填充Food和{{ 1}}。

要查询，您需要按类型从Book进行过滤。

Items

选项B每个具体类别的表格

using (var context = new AppContext())
{
    var foods = context.Items.Where(item => item is Food).ToArray();
    var books = context.Items.Where(item => item is Book).ToArray();
}

结果将是 3个表格，表格public class AppContext : DbContext { public DbSet<Person> People { get; set; } public DbSet<Food> Foods { get; set; } public DbSet<Book> Books { get; set; } protected override void OnModelCreating(DbModelBuilder modelBuilder) { modelBuilder.Entity<Person>().HasMany(p => p.Foods).WithRequired(f => f.CookedBy).WillCascadeOnDelete(false); } }，Person和Food。

要查询，您可以直接从食品和书籍中获取。

Book

选项C每类型表

using (var context = new AppContext())
{
    var foods = context.Foods.ToArray();
    var books = context.Books.ToArray();
}

结果将是 4个表格，表格public class AppContext : DbContext { public DbSet<Person> People { get; set; } public DbSet<Item> Items { get; set; } protected override void OnModelCreating(DbModelBuilder modelBuilder) { modelBuilder.Entity<Person>().HasMany(p => p.Foods).WithRequired(f => f.CookedBy).WillCascadeOnDelete(false); modelBuilder.Entity<Food>().ToTable("Foods"); modelBuilder.Entity<Book>().ToTable("Books"); } }，Person，Item和Food。表格Book和Food与表格Book有关。

查询与Table Per Hierarchy相同。

实体框架并行一对多关系

1 个答案: