EntityFramework 实体关系配置问题

Question

我想在菜单项和餐厅之间创建一种关系 - 每个菜单项可以有一个餐厅，而餐厅可以有多个菜单项，我想将其设置为一对多关系，但是在'update-database' 命令我收到错误：“在表 'MenuItems' 上引入外键约束 'FK_MenuItems_Restaurants_RestaurantId' 可能会导致循环或多个级联路径。指定 ON DELETE NO ACTION 或 ON UPDATE NO ACTION，或修改其他外键约束。 无法创建约束或索引。请参阅以前的错误。”

有什么解决办法吗？

public class Restaurant
{
    public int Id { get; set; }
    public string Name { get; set; } = string.Empty;
    public string Description { get; set; } = string.Empty;
    public string Address { get; set; } = string.Empty;
    public string PhoneNumber { get; set; } = string.Empty;
    public List<MenuItem> MenuItems { get; set; } = new List<MenuItem>();
}

 public class MenuItem
{
    public int Id { get; set; }
    public string Name { get; set; } = string.Empty;
    public string Description { get; set; } = string.Empty;
    public Restaurant Restaurant { get; set; }
    public int RestaurantId { get; set; }
}

我在 DataContext 类中像这样配置它：

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);


        modelBuilder.Entity<Restaurant>()
            .HasOne(k => k.Owner)
            .WithMany(k => k.Restaurants)
            .HasForeignKey(k => k.OwnerId)
            .OnDelete(DeleteBehavior.Cascade);

        modelBuilder.Entity<MenuItem>()
            .HasOne(k => k.Restaurant)
            .WithMany(k => k.MenuItems)
            .HasForeignKey(k => k.RestaurantId)
            .OnDelete(DeleteBehavior.NoAction);


        modelBuilder.ApplyConfigurationsFromAssembly(Assembly.GetExecutingAssembly());

    }

Answer 1

我会删除

HasOne

并将其替换为

HasRequired

并映射它的 Id。实体将自行制作外键。

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<Restaurant>()
            .HasRequired(k => k.Owner)
            .WithMany(k => k.Restaurants)
            .Map(k => k.MapKey("OwnerId"))
            .OnDelete(DeleteBehavior.Cascade);

        modelBuilder.Entity<MenuItem>()
            .HasRequired(k => k.Restaurant)
            .WithMany(k => k.MenuItems)
            .Map(k => k.MapKey("RestaurantId"))
            .OnDelete(DeleteBehavior.NoAction);


        modelBuilder.ApplyConfigurationsFromAssembly(Assembly.GetExecutingAssembly());

    }

Answer 2

我认为问题是由

Restaurant

实体和

MenuItem

实体上的级联删除操作的组合引起的。要解决此问题，您应该调整一个或两个关系的级联删除行为。

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    base.OnModelCreating(modelBuilder);

    modelBuilder.Entity<Restaurant>()
        .HasOne(k => k.Owner)
        .WithMany(k => k.Restaurants)
        .HasForeignKey(k => k.OwnerId)
        .OnDelete(DeleteBehavior.Cascade);

    modelBuilder.Entity<MenuItem>()
        .HasOne(k => k.Restaurant)
        .WithMany(k => k.MenuItems)
        .HasForeignKey(k => k.RestaurantId)
        .OnDelete(DeleteBehavior.Restrict); // Change this to Restrict

    modelBuilder.ApplyConfigurationsFromAssembly(Assembly.GetExecutingAssembly());
}