ASP.NET MVC 4引用单个父实体的多个外键

Question

我正在尝试开发一个ASP.NET MVC 4应用程序,玩家可以根据他们的进攻,防守和助攻技能进行评分.攻击,防御和辅助是引用相同查找表的Player表上的外键 - 评级.

我有以下父实体:

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

    public string Name { get; set; }

    public virtual ICollection<Player> Players { get; set; }
}

和子实体:

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

    public string Name { get; set; }

    public int OffenceRatingId { get; set; }
    [ForeignKey("OffenceRatingId")]
    public virtual Rating OffenceRating { get; set; }

    public int DefenceRatingId { get; set; }
    [ForeignKey("DefenceRatingId")]
    public virtual Rating DefenceRating { get; set; }

    public int AssistRatingId { get; set; }
    [ForeignKey("AssistRatingId")]
    public virtual Rating AssistRating { get; set; }
}

建筑和脚手架很好但是当我运行应用程序时,我收到以下错误:

Introducing FOREIGN KEY constraint 'FK_dbo.Players_dbo.Ratings_DefenceRatingId' on table 'Players' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.

我是MVC的新手,不知道我在这里缺少什么.任何有关这方面的帮助将不胜感激.谢谢.

Answer 1

默认情况下,Entity Framework具有Cascade on Delete约定.当两个实体彼此具有外键时,它会导致循环引用,并且删除时级联不能应用于两个实体.

最简单的解决方案是删除删除约定上的级联,并根据具体情况应用它.