在Entity Framework中插入具有多对多关系的新对象 [英] Inserting new object with many to many relationship in Entity Framework

问题描述

我有一个json对象的电影，我传递给我的控制器。

  {data：[{
 Id：12345，
标题：'Movie1'，
年：2010，
字符：[{
名称：'Character1'，
个人：{Id：1，Name：'Person1'} 
}，{
名称：'Character2'，
个人：{Id：2，Name：'Person2'} 
}] 
}]} 
  pre> 
 
 
模型绑定工作正常，但我有一个问题，通过实体将每个电影插入数据库框架5.当插入电影的每个 Person 时，我遇到主键违规。
 
 
 
我了解为什么会这样发生。添加新的电影时，有些人已经存在于数据库中，以便发生违规。每个人的Id不是自动生成的。我正在使用我从api收到的Id，我得到的信息。 
 
 
 
 A 电影与 Person ， Character 是两者之间的桥梁。
  public class Movie {
 public int Id {get;组; } 
 public string标题{get;组; } 
 public int？年{get;组; } 
 public virtual ICollection< Character>人物{get;组; } 
 
 public Movie（）{
 Characters = new HashSet< Character>（）; 
} 
} 
 
 public class Character {
 public string Name {get;组; } 
 public virtual Movie Movie {get;组; } 
 public virtual Person Person {get;组; } 
} 
 
 public class Person {
 public int Id {get; set; } 
 public string Name {get;组; } 
 public virtual ICollection< Character>人物{get;组; } 
 
 public Person（）{
 Characters = new HashSet< Character>（）; 
} 
} 
  
我的问题是...我知道我可以循环通过每个 Person 对象和 Attach（）（如果它存在）或 Add（）如果没有。 可以实体框架自动处理插入新的 Person 并忽略它（如果它已经存在）如果没有，这种类型的问题最好的做法是什么？ 
解决方案
我认为没有必要附加Person对象，如果它们已经存在。 
 
 
 
我会做的是循环遍历API Person对象并与EF DbContext进行比较。
  var dbPerson = MyMovieContext.Persons.Where（x => x.ID == myPersonID）.SingleOrDefault（）; 
  
如果找不到匹配项，则添加。如果你找到一个匹配项，然后用DbContext替换Character上的Entity引用。
 
I have a json object of Movies that I'm passing to my controller. 
{data : [{
    Id: 12345,
    Title: 'Movie1',
    Year: 2010,
    Character: [{
        Name: 'Character1',
        Person: { Id: 1, Name: 'Person1' }
    },{
        Name: 'Character2',
        Person: { Id: 2, Name: 'Person2' }
    }]
}]}
The model binding is working fine but I'm having an issue inserting each Movie into the database via Entity Framework 5. I'm getting a primary key violation when each Person for a movie is being inserted.

I understand why this is happening. Some people already exist in the database when adding a new Movie so the violation occurs. The Id for each person is not auto generated. I'm using the Id that I receive from the api I get the information from. 

A Movie has a many-to-many relationship with Person, with Character being the bridge between the two.
public class Movie {
    public int Id { get; set; }
    public string Title { get; set; }
    public int? Year { get; set; }
    public virtual ICollection<Character> Characters { get; set; } 

    public Movie() {
        Characters = new HashSet<Character>();
    }
}

public class Character {
    public string Name { get; set; }    
    public virtual Movie Movie { get; set; }    
    public virtual Person Person { get; set; }
}

public class Person {
    public int Id { get;set; }
    public string Name { get; set; }
    public virtual ICollection<Character> Characters { get; set; }

    public Person() {
        Characters = new HashSet<Character>();
    }
}
My question is... I know I can loop through each Person object and Attach() if it exists or Add() if it doesn't. Can Entity Framework automatically handle inserting a new Person and ignore it if it already exists? If not, what is the best practice for this type of problem?
解决方案
I believe it is unnecessary to Attach the Person objects if they already exist.  

What I would do is loop through the API Person objects and compare with the EF DbContext.
var dbPerson = MyMovieContext.Persons.Where(x => x.ID == myPersonID).SingleOrDefault();
If you don't find a match, then Add.  If you do find a match, then replace the reference on Character with the Entity from the DbContext.

                        
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