[英]Difficulty only mapping base class in Entity Framework
I'm having difficulty figuring out how to only map a base class in Entity Framework to my database, while preventing any information about classes that inherit it from being mapped to the database. 我很难弄清楚如何仅将Entity Framework中的基类映射到我的数据库,同时防止有关继承它的类的任何信息映射到数据库。
I created a simple example to highlight my difficulty where there is a base Worker
class, and a child class called Engineer
. 我创建了一个简单的示例来突出说明我的困难,即存在一个基本的Worker
类和一个名为Engineer
的子类。 For some reason, assume that I don't care to store details of the engineer... I only want my database to contain the information in the Worker
class. 出于某种原因,假设我不在乎存储工程师的详细信息...我只希望我的数据库将信息包含在Worker
类中。
So I've done the following: 所以我做了以下工作:
class Program
{
static void Main(string[] args)
{
Engineer e = new Engineer();
e.Name = "George";
e.Focus = "Software";
MyDatabase db = new MyDatabase();
e.Save(db);
}
}
public class MyDatabase : DbContext
{
public DbSet<Worker> Workers { get; set; }
public MyDatabase() : base("mytempdb") { }
}
[NotMapped]
public class Engineer : Worker
{
public string Focus { get; set; }
}
public class Worker
{
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
public string Name { get; set; }
public bool Save(MyDatabase db)
{
try
{
if (db.Workers.Any(w => w.ID == this.ID))
{
db.Workers.Attach(this);
db.Entry(this).State = System.Data.Entity.EntityState.Modified;
}
else
{
db.Workers.Add((Worker)this);
}
db.SaveChanges();
}
catch (Exception e)
{
Console.WriteLine(e);
return false;
}
return true;
}
}
I am doing "Database First" design, and my database table looks like: 我正在做“数据库优先”设计,我的数据库表如下所示:
CREATE TABLE [dbo].Workers
(
[ID] INT NOT NULL PRIMARY KEY,
[Name] NVARCHAR(200) NULL,
[Discriminator] NVARCHAR(200) NULL
)
However, when I run my program, it is still looking for a entity to store Engineer
in. I've told it not to map it, hoping that it would only map the base class to the database: 但是,当我运行程序时,它仍在寻找要存储Engineer
的实体。我告诉它不要映射它,希望它只会将基类映射到数据库:
System.InvalidOperationException: Mapping and metadata information could not be found for EntityType 'ConsoleApplication10.Engineer'. System.InvalidOperationException:找不到EntityType'ConsoleApplication10.Engineer'的映射和元数据信息。
I think you might have to map the entity to a new Worker
entity before saving so that entity framework doesn't look for the object's sub type— Engineer
. 我认为您可能必须在保存之前将实体映射到新的Worker
实体,以便实体框架不会查找对象的子类型Engineer
。
For example: 例如:
public class Worker
{
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
public string Name { get; set; }
public static FromWorker(Worker worker)
{
// example of mapping the entity
return new Worker
{
ID = worker.ID,
Name = worker.Name,
};
}
public bool Save(MyDatabase db)
{
try
{
Worker worker = Worker.FromWorker(this);
if (db.Workers.Any(w => w.ID == worker.ID))
{
db.Workers.Attach(worker);
db.Entry(worker).State = System.Data.Entity.EntityState.Modified;
}
else
{
db.Workers.Add(worker);
}
db.SaveChanges();
}
catch (Exception e)
{
Console.WriteLine(e);
return false;
}
return true;
}
}
EDIT: You already use [NotMapped] 编辑:您已经使用[NotMapped]
I did not see that first time sorry. 我没有看到第一次抱歉。 So i dont expect it to be in the model. 所以我不希望它出现在模型中。
There is a do not map attribute for properties and equivalent fluent api option for whole classes. 属性没有“不映射”属性,整个类没有等效的fluent api选项。
[NotMapped]
public string BlogCode { get;set; }
and for a POCO inside the Context 对于上下文中的POCO
public class MyDbContext : DbContext {
protected override void OnModelCreating(DbModelBuilder modelBuilder) {
//Tell EF not to include these in DB. Ignore these please
// Anthing that EF picks and generates a table for that shoudl not be persisted
// modelBuilder.Ignore<EFpleaseIgnoreMe>();
modelBuilder.Ignore<YourType>();
}
}
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