Question

我有一个非常简单的架构，针对这个问题进一步简化

Table: Airport
IATA char(3) Primary Key
Name varchar(20)

Table: Airport_Terminal
IATA char(3) (comp key1)
TerminalName (comp key2)

POCOs
public sealed class Airport
{
    [Key]
    public string IATA { get; set; }       

    public string Name { get; set; }

    public ICollection<AirportTerminal> Terminals { get; set; }
}

    public class AirportTerminal
{
    [Key, Column(Order = 0)]
    public string IATA { get; set; }

    [Key, Column(Order = 1)]
    public string Terminal { get; set; }

    public Airport Airport { get; set; }

}

AirportTerminal配置

modelBuilder.Entity<AirportTerminal>()
    .HasOptional<Airport>(s => s.Airport)
    .WithMany(s => s.Terminals)
    .HasForeignKey(s => s.IATA);

有些机场（在我的应用程序中）有多个终端，有些则没有。当为给定机场定义了终端时，我只想对Terminals属性做出反应。如果我为每个机场输入一条记录，则此配置有效。但是当我试图查找任何机场时，我得到：

 "One or more validation errors were detected during model generation: Multiplicity conflicts with the referential constraint in Role 'AirportTerminal_Airport_Target' in relationship 'AirportTerminal_Airport'. Because all of the properties in the Dependent Role are non-nullable, multiplicity of the Principal Role must be '1'."

研究表明，当可选成员上存在非可空属性时会发生此错误，因此无法将其设置为null。 AirportTerminal包含两个字符串，可以为空。

有什么想法吗？

Answer 1

考虑仅使用表的键。这是最好的而不是多个键。放置索引约束以确保属性IATA和Terminal中的唯一性。

波苏斯：

public sealed class Airport
{
    [Key]
    public Guid Id { get; set; }

    public string IATA { get; set; }       

    public string Name { get; set; }

    public ICollection<AirportTerminal> Terminals { get; set; }
}

public class AirportTerminal
{
    [Key]
    public Guid Id { get; set; }

    public string IATA { get; set; }

    public string Terminal { get; set; }

    public Airport Airport { get; set; }

    public Guid? AirportId { get; set; }
}

配置：

modelBuilder.Entity<AirportTerminal>()
    .HasOptional<Airport>(s => s.Airport)
    .WithMany(s => s.Terminals)
    .HasForeignKey(s => s.AirportId);

EF可选一对多重误差

1 个答案: