使用表每类型继承时无法添加数据 [英] Unable to add data while using Table Per Type Inheritance

问题描述

您好。在我的模型中，我有一个名为Person and Learner的实体，而Teacher则从Person继承。当我尝试为学习者添加数据时：

 使用（ var  db =  new  SCSOMLAModelContext（））
 {
  var  learner =  new 学习者
 {
 FirstName = firstName，
 MiddleName = middleName ，
 LastName = lastName，
 UserId =  1 ，
 RegistrationNumber = registrationNumber 
}; 
 
 db。 
 
} 

上下文对象db，似乎不包含有关继承类型的信息：

  public   class  SCSOMLAModelContext：DbContext 
 {
  public  SCSOMLAModelContext（）; 
 
  public   virtual  DbSet< Person>人{获取;  set ; } 
  public   virtual  DbSet< User>用户{获取;  set ; } 
 
 受保护 覆盖  void  OnModelCreating（DbModelBuilder modelBuilder）; 
} 

我使用Model First方法，没有这个实体（学习者和老师），我无法添加数据给他们。在我的数据库中，我将这些表格显示为People_Learner和People_Teacher。



请协助如何将数据添加到此表中，我完全陷入困境。为什么这两个实体（学习者和教师）不在DbContext上？我正在使用VS2013。

解决方案

你应该这样写..

  using （ var  db =  new  SCSOMLAModelContext（））
 {
  var  learner =  new 学习者
 {
 FirstName = firstName，
 MiddleName = middleName，
 LastName = lastName，
 UserId =  1 ，
 RegistrationNumber = registrationNumber 
}; 
 
 db.Learners.AddObject（学习者）; 
 db.SaveChanges（）; 
 
} 

这会将记录插入学习者表格。

< blockquote>问题在于，正如我所说，Model First不会在DbContext中添加派生类（Learner和Teacher）。我为DbContext继承类所做的更改是：

  public   partial   class  SCSOMLAModelContext：DbContext 
 {
  public  SCSOMLAModelContext（）
： base （  name = SCSOMLAModelContext）
 {
} 
 
  protected  < span class =code-keyword> override   void  OnModelCreating（DbModelBuilder modelBuilder）
 {
  modelBuilder.Entity<学习者>（）。ToTable（  User）; 
 modelBuilder.Entity< Teacher>（）。ToTable（  Person）;  
} 
 
  public   virtual  DbSet< User>用户{获取;  set ; } 
  public   virtual  DbSet< Person>人{获取;  set ; } 
   public   virtual  DbSet< Learner>学习者{获取;  set ; } 
  public   virtual  DbSet< Teacher>教师{获取;  set ; }  
} 

它有效！ ： - ）

Hi. In my model, I have an entity called Person and Learner and Teacher inherit from Person. When I attempt to add data for a Learner as thus:

using (var db = new SCSOMLAModelContext())
            {
                var learner = new Learner
                {
                    FirstName = firstName,
                    MiddleName = middleName,
                    LastName = lastName,
                    UserId = 1,
                    RegistrationNumber = registrationNumber
                };

                db.

            }

the context object "db", seem not to contain information about the inheritance types as thus:

public class SCSOMLAModelContext : DbContext
    {
        public SCSOMLAModelContext();

        public virtual DbSet<Person> People { get; set; }
        public virtual DbSet<User> Users { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder);
    }

I am using Model First approach and without this entities (Learner and Teacher), I am unable to add data to them. In my database, I have this tables available as "People_Learner", and "People_Teacher".

Please assist on how to add data to this tables, I am totally stuck. And why are these two entities (Learner and Teacher) not on DbContext? I am using VS2013.

解决方案

you should write like this..

using (var db = new SCSOMLAModelContext())
            {
                var learner = new Learner
                {
                    FirstName = firstName,
                    MiddleName = middleName,
                    LastName = lastName,
                    UserId = 1,
                    RegistrationNumber = registrationNumber
                };

                db.Learners.AddObject(learner);
                db.SaveChanges();

            }

this will insert record to the Learner table.

The problem is that, as I had said, Model First does not add the derived classes (Learner and Teacher) in DbContext. The changes I made for the DbContext inheriting class is this:

public partial class SCSOMLAModelContext : DbContext
    {
        public SCSOMLAModelContext()
            : base("name=SCSOMLAModelContext")
        {
        }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Learner>().ToTable("User");
            modelBuilder.Entity<Teacher>().ToTable("Person");
        }

        public virtual DbSet<User> Users { get; set; }
        public virtual DbSet<Person> People { get; set; }
        public virtual DbSet<Learner> Learners { get; set; }
        public virtual DbSet<Teacher> Teachers { get; set; }
    }

It works! :-)

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