EntityFramework 核心 SQLite 与列表<t>覆盖当前 ID 值而不是添加下一个 ID</t>

Question

I have Models:

  public class TVProgram
    {
        [Key]
        public int Id { get; set; }
        public string Name { get; set; }
        public List<Channel> Channels { get; set; }

    }
    

  public class Channel
    {
        [Key]
        public int Id { get; set; }
        public string Name { get; set; }
        public int Created { get; set; }
    }

When i saved data to database it should be a lot of TV Channels connected to specify TVPrograms.

For example i need to have program named "Animals Life" on Channels "Discovery, Animal Pl.net, BBC", but in database its saved with last added id, for example:

ID   |  Name  |  TVProgramID
0    | AL     |      4    
0    | AL2    |      4    

Where 4 is id of last updated Program TV.

I expect something like

ID   |  Name  |  TVProgramIDs
0    | AL     |      1,2,3    
0    | AL2    |      2,4,9    

Im using context like:

using(var cnx = new MyContext())
{
    var channel = cnx.Channels.Where(x => x.Name == "AL").FirstOrDefault();
    var program = cnx.Programs.Where(x => x.Name == "Discovery").Include(x=>x.Channels).FirstOrDefault();
    
    program.Channels.Add(channel);
    program.SaveChanges();
}

How to fix that?

Answer 1

You are missing a 'many to many' table between TVProgram and Channel. In EF this is (or used to be) automatic, but in EF core you need to do this manually.

public class TVProgram
{
    [Key]
    public int Id { get; set; }
    public string Name { get; set; }
    public List<TVProgramChannel> TVProgramChannels { get; set; }
}


public class Channel
{
    [Key]
    public int Id { get; set; }
    public string Name { get; set; }
    public int Created { get; set; }
    public List<TVProgramChannel> TVProgramChannels { get; set; }
}

public class TVProgramChannel
{
    public TVProgram TVProgram {get;set;}
    public Channel Channel {get;set;}
}