Question

我创建了一个非常简单的项目来演示每个层次结构表的不一致性。在我试图生成数据库的单元测试中，我得到了许多错误之一，具体取决于配置：

没有Required()方法

Map<InActiveUser>(x => x.Requires("IsActive").HasValue(false));
Map<ActiveUser>(x => x.Requires("IsActive").HasValue(true));

提供了：

System.Data.DataException : An exception occurred while initializing the database. See the InnerException for details.
  ----> System.Data.EntityCommandCompilationException : An error occurred while preparing the command definition. See the inner exception for details.
  ----> System.Data.MappingException : 
(6,10) : error 3032: Problem in mapping fragments starting at line 6:Condition member 'User.IsActive' with a condition other than 'IsNull=False' is mapped. Either remove the condition on User.IsActive or remove it from the mapping.

使用Required()方法：

Map<InActiveUser>(x => x.Requires("IsActive").HasValue(false).IsRequired());

Map<ActiveUser>(x => x.Requires("IsActive").HasValue(true).IsRequired());

提供了：

System.Data.DataException : An exception occurred while initializing the database. See the InnerException for details.
  ----> System.Data.EntityCommandCompilationException : An error occurred while preparing the command definition. See the inner exception for details.
  ----> System.Data.MappingException : 
(6,10) : error 3023: Problem in mapping fragments starting at lines 6, 13, 19:Column User.IsActive has no default value and is not nullable. A column value is required to store entity data.

根据我的理解，我们不应该在基类型上定义鉴别器列/属性，但无论是否定义了列，它似乎都没有区别：

  public class User
  {
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public virtual int Id { get; set; }

    [Required]
    public virtual string Username { get; set; }

    [Required]
    [DefaultValue(true)]
    public bool IsActive { get; set; } //have tried without this property
  }

  public class InActiveUser : User
  {
    public virtual DateTime DeActivatedDate { get; set; }
  }

  public class ActiveUser : User
  {
  }

Answer 1

您无法将鉴别器映射为实体中的属性。 Discriminator定义实体的类型。原因很清楚 - 鉴别器定义了实例类型。如果您能够在运行时更改鉴别器值，会发生什么？ .NET应如何更改实例化对象的类型？

将实体定义为：

public class User
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public virtual int Id { get; set; }

    [Required]
    public virtual string Username { get; set; }
}

public class InActiveUser : User
{
    public virtual DateTime DeActivatedDate { get; set; }
}

public class ActiveUser : User
{ }

这应该有效：

modelBuilder.Entity<User>()
            .Map<InActiveUser>(x => x.Requires("IsActive").HasValue(false))
            .Map<ActiveUser>(x => x.Requires("IsActive").HasValue(true));

EF4.1异常创建具有每层次表继承的数据库

1 个答案: