多个“1至0..1”关系模型 [英] multiple "1 to 0..1" relationship models

问题描述

我正在使用这个教程从微软创建与EF4.1的一对一关系在教师和OfficeAssignment之间。但是现在我想为每位讲师添加一个主页（1到零或-1），如下所示：

我添加了与OfficeAssignment完全相同的Home模型（如上面的教程），但是当我尝试添加这些模型的控制器时，我得到错误已添加相同名称的项目。

所以我的模型设置不正确。
下面有什么问题？
如何在EF4.1中创建多个一对一关系？

  public class Instructor 
 {
 public Int32 InstructorID {get;组; } 
 public string LastName {get;组; } 
 public string FirstMidName {get;组; } 
 public virtual OfficeAssignment OfficeAssignment {get;组; } 
 public virtual Home首页{get;组; 
} 
 
 public class OfficeAssignment 
 {
 [Key] 
 public int InstructorID {get;组; } 
 public string Location {get;组; } 
 public virtual Instructor Instructor {get;组; 
} 
 
 public class Home 
 {
 [Key] 
 public int InstructorID {get;组; } 
 public string Location {get;组; } 
 public virtual Instructor Instructor {get;组; } 
} 
 
 public class上下文：DbContext 
 {
 public DbSet< OfficeAssignment> OfficeAssignments {get;组; } 
 public DbSet< Instructor>导师{get;组; } 
 public DbSet< Home>家园组; 
 
 protected override void OnModelCreating（DbModelBuilder modelBuilder）
 {
 
 modelBuilder.Conventions.Remove< PluralizingTableNameConvention>（）; 
 modelBuilder.Entity< Instructor>（）
 .HasOptional（p => p.OfficeAssignment）
 .WithRequired（p => p.Instructor）; 
 modelBuilder.Entity< Instructor>（）
 .HasOptional（p => p.Home）.WithRequired（p => p.Instructor）; 
} 
  

解决方案

看起来不像EF支持实际1到0..1的关系。你需要一个外键并将可选（int？）添加到主模型中。

所以我做了如下，它的作用就像一个魅力。

  public class Instructor 
 {
 public Int InstructorID {get;组; } 
 public string LastName {get;组; } 
 public string FirstMidName {get;组; } 
 
 public int？ OfficeAssignmentID {get;组; } 
 public virtual OfficeAssignment OfficeAssignment {get;组; } 
 
 public int？ HomeID {get;组; } 
 public virtual Home首页{get;组; 
 
} 
 
 public class OfficeAssignment 
 {
 public int OfficeAssignmentID {get;组; } 
 public string Location {get;组; } 
 
} 
 
 public class Home 
 {
 public int HomeID {get;组; } 
 public string Location {get;组; } 
} 
  

I am using this tutorial from microsoft to create a one-zero-to-one relationship with EF4.1 Between an Instructor and OfficeAssignment. This is working like a charm.

But now I want to add a Home for each Instructor (1 to zero-or-1) like in this:

I added the Home model exactly the same way as the OfficeAssignment (like in the tutorial above), but when I try to add controllers for these model, I get the error "An item with the same name has already been added".

So my model is set up incorrectly. What is wrong with the below? How do I create multiple one-to-zero-to-one relationships in EF4.1?

public class Instructor
{
    public Int32 InstructorID { get; set; }
    public string LastName { get; set; }
    public string FirstMidName { get; set; }
    public virtual OfficeAssignment OfficeAssignment { get; set; }
    public virtual Home Home { get; set; }
}

public class OfficeAssignment
{
    [Key]
    public int InstructorID { get; set; }
    public string Location { get; set; }
    public virtual Instructor Instructor { get; set; }
}

public class Home
{
    [Key]
    public int InstructorID { get; set; }
    public string Location { get; set; }
    public virtual Instructor Instructor { get; set; }
}

public class Context : DbContext
{
    public DbSet<OfficeAssignment> OfficeAssignments { get; set; }
    public DbSet<Instructor> Instructors { get; set; }
    public DbSet<Home> Homes { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {

          modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
          modelBuilder.Entity<Instructor>()
            .HasOptional(p => p.OfficeAssignment)
            .WithRequired(p => p.Instructor);
          modelBuilder.Entity<Instructor>()
             .HasOptional(p => p.Home).WithRequired(p => p.Instructor);
}

解决方案

Doesn't look like EF supports real 1 to 0..1 relationship. You need a foreign key. And add the optional (int?) into the main model.

So I did this as follow, and it works like a charm.

public class Instructor
{
    public Int InstructorID { get; set; }
    public string LastName { get; set; }
    public string FirstMidName { get; set; }

    public int? OfficeAssignmentID { get; set; }
    public virtual OfficeAssignment OfficeAssignment { get; set; }

    public int? HomeID { get; set; }
    public virtual Home Home { get; set; }

}

public class OfficeAssignment
{
    public int OfficeAssignmentID { get; set; }
    public string Location { get; set; }

}

public class Home
{
    public int HomeID { get; set; }
    public string Location { get; set; }
}

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