Entity Framework 6 Context duplicate while query

Question

I have some issue that I can not solve. In my project I use EF6 Code First. I've created some models, but the head of them is User model:

 public class User
{
    [Required]
    public Guid Id { get; set; }
    [Required, MaxLength(20), MinLength(5), UniqProp] 
    public string Login { get; set; }
    [Required, MaxLength(20), MinLength(8)]
    public string Password { get; set; }
    [Required]
    public Role Role { get; set; }
    [Required]
    public string FirstName { get; set; }
    [Required]
    public string LastName { get; set; }
    [Required, UniqProp]
    public string Email { get; set; }
    [Required]
    public string City { get; set; }
    public virtual List<Ticket> Tickets { get; set; } 
}

Also I've created my own context as shown below:

public class TheatreContext : DbContext
{
    public DbSet<User> Users { get; set; }
    public DbSet<Role> Roles { get; set; }
    public DbSet<Ticket> Tickets { get; set; }
    public DbSet<Play> Plays { get; set; }
}

After this I initialise my db in this way:

 using (var db = new TheatreContext())
 {
      Adding objects to db and save changes.
 }

At that moment everything works fine. All data was added to database. Then I've decided created my Repository class to make some operations with db:

public class TheatreRepository<T> : IRepository<T> where T: class
{
    private readonly TheatreContext _context;
    private readonly DbSet<T> _dbSet;

    public TheatreRepository()
    {
        _context = new TheatreContext();
        _dbSet = _context.Set<T>();
    }

    public void Add(T entity)
    { 
        _dbSet.Add(entity);
    }

    public DbSet<T> GetAll()
    {
        return this._dbSet;
    }

    public void Commit()
    { 
        _context.SaveChanges();
    }

And when I try to add new User in this way:

var repo = new TheatreRepository<User>();
var roleRepo = new TheatreRepository<Role>();

var newUser = new User
                  {
                      Id = Guid.NewGuid(),
                      Login = "Lionqweq",
                      City = "Minsk",
                      Role = roleRepo.GetAll().First(role => role.RoleType == RoleType.User),
                      FirstName = "Alex",
                      Email = "[email protected]",
                      Password = "dsas1qsqda",
                      LastName = "Ivanov"
                  };
repo.Add(newUser);
repo.Commit();

While calling Commit (SaveChanges in db) it throws DbUpdateException because I try to add to Role table object with existing Id. It doesn't make sense for me! Actually I didn't add any role, I've tried to add User only.

That what my Role table locally contains:

And that what I have in my Users table locally:

enter image description here

Please any suggestions and ideas! I got confused deeply

dany · Accepted Answer · 2015-05-27 09:53:49Z

1

You should try instead of

[Required]
public Role Role { get; set; }

To use also use a reference to the FK:

[Required]
public Guid RoleId { get; set; }
public virtual Role Role { get; set; }

When you create the a new user set only the RoleId

here is an example: EF first code

answered May 27, 2015 at 9:53

dany

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1 Comment

Dmitry Koshevoy Over a year ago

Dear dany, thank you! You've helped me greatly! I've solved it in this way: public Guid RoleId { get; set; } [ForeignKey("RoleId")] public virtual Role Role { get; set; }

Sherif Ahmed · Accepted Answer · 2015-05-27 09:59:11Z

1

your problem is here

public TheatreRepository()
{
    _context = new TheatreContext();
    _dbSet = _context.Set<T>();
}

if you are implementing a repository pattern then your repository class must get the context in the constructor Which is know as DI, so it must be like that

public TheatreRepository(TheatreContext context)
{
    _context = context;
    _dbSet = _context.Set<T>();
}

Explanation:

the repositories must use the same context to keep tracking of changes happening and loaded (local) entities so consider declaring your context before the repositories as below:

var db = new TheatreContext();
var repo = new TheatreRepository<User>(db);
var roleRepo = new TheatreRepository<Role>(db);
var newUser = new User
{
    Id = Guid.NewGuid(),
    Login = "Lionqweq",
    City = "Minsk",
    Role = roleRepo.GetAll().First(role => role.RoleType == RoleType.User),
    FirstName = "Alex",
    Email = "[email protected]",
    Password = "dsas1qsqda",
    LastName = "Ivanov"
};
repo.Add(newUser);
repo.Commit();

edited May 27, 2015 at 9:59

answered May 27, 2015 at 9:45

Sherif Ahmed

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2 Comments

Rup Over a year ago

Are you saying they should both use the same instance of TheatreContext? (which isn't completely implied by 'must be dependency-injected')

Dmitry Koshevoy Over a year ago

So it means I can have only one context once created for all Repositories? If I'm right it means that for each table I will store my data Local too and I'll take quite much resources

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