如何重写基类字段功能
本文关键字:基类 字段 功能 重写 何重写 | 更新日期: 2023-09-27 18:21:44
好吧,我有BaseModel
public class BaseModel
{
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int Id { get; set; }
public bool Deleted { get; set; }
}
我也有模型Update
public class Update : BaseModel
{
public DateTime Updated { get; set; }
}
它源自BaseModel
BaseModel
Id
字段中没有递增,但对于Update
模型,我需要Id
Identity
.
我可以向Update
添加新字段,例如UpdateId
,这将递增,但删除字段Id
?
有没有可能的解决方案?
:如何以另一种方式声明模型
public class BaseModel
{
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int Id { get; set; }
public bool Deleted { get; set; }
}
和
public class Update : BaseModel
{
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
public DateTime Updated { get; set; }
}
Update
中的Id
将覆盖BaseModel
中的Id
可以使用以下技术(在 Windows 窗体控件中大量使用,以将不同的属性应用于同一属性(:
public class BaseModel
{
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public virtual int Id { get; set; }
public bool Deleted { get; set; }
}
public class Update : BaseModel
{
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public override int Id { get { return base.Id; } set { base.Id = value; } }
public DateTime Updated { get; set; }
}
在上下文类(继承自 DbContext
(中,可以通过重写 OnModelCreating
方法重写Update
实体的设置,如下所示:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<Update>()
.Property(x => x.Id)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
}
引用此参考资料:
您可以使用数据注释或流畅的 API 进一步配置模型。通过流畅的 API 为配置提供优先级,然后是数据注释,然后是约定。
这意味着您可以使用流畅的 API 覆盖数据注释配置(通过 OnModelCreating
(。
好吧,您可以在
UpdateModel
中隐藏BaseModel
的 ID
public class UpdateModel : BaseModel
{
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public new int Id { get; set; }
public DateTime Updated { get; set; }
}
编辑
根据注释,从编程的角度来看,上述解决方案是完全错误的,因为如果您将从UpdateModel
派生的任何实体转换为BaseModel
,则支持字段Id
将为空,尽管它将编译并给出所需的结果。
检查以下解决方案
public class BaseEntity
{
public int Id { get; set; }
public bool Deleted { get; set; }
}
public class UpdateEntity : BaseEntity
{
public DateTime Updated { get; set; }
}
public class Entity1 : BaseEntity
{
public string Name { get; set; }
}
public class Entity2 : UpdateEntity
{
public string Name { get; set; }
}
public abstract class BaseEntityTypeConfiguration<T> : EntityTypeConfiguration<T>
where T : BaseEntity
{
public BaseEntityTypeConfiguration()
{
Property(x => x.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
}
}
public abstract class UpdateEntityTypeConfiguration<T> : EntityTypeConfiguration<T>
where T : UpdateEntity
{
public UpdateEntityTypeConfiguration()
{
Property(x => x.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
}
}
public class Entity1Configuration : BaseEntityTypeConfiguration<Entity1>
{
public Entity1Configuration()
: base()
{
Property(x => x.Name).HasMaxLength(100);
}
}
public class Entity2Configuration : UpdateEntityTypeConfiguration<Entity2>
{
public Entity2Configuration()
: base()
{
Property(x => x.Name).HasMaxLength(100);
}
}
public class MyDbContext : DbContext
{
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
var typesToRegister = from type in Assembly.GetExecutingAssembly().GetTypes()
where !string.IsNullOrEmpty(type.Namespace) &&
type.BaseType != null &&
type.BaseType.IsGenericType
let genericType = type.BaseType.GetGenericTypeDefinition()
where genericType == typeof(BaseEntityTypeConfiguration<>) || genericType == typeof(UpdateEntityTypeConfiguration<>)
let genericArgument = type.BaseType.GetGenericArguments().FirstOrDefault()
where genericArgument != null && genericArgument.BaseType != null &&
(genericArgument.BaseType == typeof(BaseEntity) || genericArgument.BaseType == typeof(UpdateEntity))
select type;
foreach (var type in typesToRegister)
{
dynamic configurationInstance = Activator.CreateInstance(type);
modelBuilder.Configurations.Add(configurationInstance);
}
base.OnModelCreating(modelBuilder);
}
}