Models with List<> in them .. How does this work with Entity Framework?

Question

I'm new to ASP.NET, and am wondering how to create CRUD pages for a Model which has Lists of other Models ? I followed this tutorial, which creates CRUD pages for a simple scenario in which the Model has primitive data types only. So as such, the DbContext created is only for that one Model used in the tutorial. But what if I have two Models which have a One-to-Many relationship between them, such as the following scenario ?

public class Player
{
    public string name {get; set;}
    public int age {get; set;}
    public double salary {get; set;}
    public string gender {get; set;}
    public DateTime contractSignDate {get; set;}
}

public class Team
{
    public string teamName {get; set;}
    public string sportPlayed {get; set;}
    public List<Player> players {get; set;}
}

If I want to create CRUD pages for the Team Model, the DbContext I make for it refers to that Model only. In fact, VS2013's scaffolding engine doesn't even both with the players List and simply ignores it outright.

How to solve this ?

This is the DbContext I made for the Team Model:

public class TeamDBContext : DbContext
{
    public DbSet<Team> Teams { get; set; }
}

Are you trying to get automatic scaffolding for a 1-to-many relationship? — Praveen Paulose, Apr 02 '15 at 20:57
@Praveen .. Automatic would be preferred as I'm new, but if there's a standard manual procedure for accomplishing, please share that and I can try it. — Ahmad, Apr 02 '15 at 20:58

score 2 · Accepted Answer · edited Nov 15 '19 at 14:07

First, I would define the Player class as follows:

public class Player
{
  //you need to define an identifier
  public int PlayerId {get;set;}

  public string Name {get; set;}
  public int Age {get; set;}
  public double Salary {get; set;}
  public string Gender {get; set;}
  public DateTime ContractSignDate {get; set;}

  //you need a foreignkey
  [ForeignKey("TeamId")]
  public Team Team {get;set;}
  public int TeamId {get;set;}
}

And Team class:

public class Team
{
   //you need an identifier
   public int TeamId {get;set;}

   public string TeamName {get; set;}
   public string SportPlayed {get; set;}
   public List<Player> Players {get; set;}
}

And your dbcontext file:

public class TeamDBContext : DbContext
{
    public DbSet<Team> Teams { get; set; }
    public DbSet<Player> Players { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Player>()
                    .HasRequired(p => p.Team)
                    .WithMany(t => t.Players)
                    .HasForeignKey(p => p.TeamId)
    }
}

And, here is how you would a new team and player:

TeamDBContext db = new TeamDBContext();

//create a new player
Player p = new Player() {Name="make", Age=10, Salary=10, Gender="m" };
db.Players.Add(p);
db.SaveChanges();

//create a new team
Team t = new Team () {TeamName="barcelona", SportType="soccer"};
db.Teams.Add(t);
db.SaveChanges();

//add a player to a team
db.Teams.Include("Players").Players.Add(p);
db.SaveChanges();

score 0 · Answer 2 · answered Apr 02 '15 at 21:00

First of all you will need to include Player in your DBContext:

public class TeamDBContext : DbContext
{
    public DbSet<Team> Teams { get; set; }
    public DbSet<Player> Players { get; set; }
}

Then you might read this article that describes how to load related entities.

Probably you will add it like that:

public class Team
{
    public string teamName {get; set;}
    public string sportPlayed {get; set;}
    public virtual ICollection<Player> players {get; set;}
}

score 0 · Answer 3 · answered Sep 23 '19 at 16:15

public class Player
{
    public string name {get; set;}
    public int age {get; set;}
    public double salary {get; set;}
    public string gender {get; set;}
    public DateTime contractSignDate {get; set;} 
    public IList<TeamPlayer> Team { get; set; }
}

public class Team
{
    public string teamName {get; set;}
    public string sportPlayed {get; set;}
    public List<TeamPlayer> players {get; set;}
}

create new class

public class TeamPlayer 
{

    public int PlayerId { get; set; }
    public Playler Player { get; set; }

    public int TeamId { get; set; }
    public Team Team { get; set; }
}

DbContext:

    protected override void OnModelCreating(ModelBuilder constructor)
    {
        constructor.Entity<TeamPlayer >().HasKey(uc => new { uc.PlayerId, uc.TeamId });
        base.OnModelCreating(constructor);
    }

Models with List<> in them .. How does this work with Entity Framework?

3 Answers3