Entity Framework Adding Duplicate Values

Question

I am new to EF and I am trying to work with a many-to-many relationship.

I have a Developers table and I have a Applications table.

Each developer can have many applications, and each application can have many developers.

I have tried to follow examples on StackOverflow where it mentions to attach, but I've tried everything and it still creates duplicate developers for an application.

public class Developer 
    {
        public int DeveloperId { get; set; }
        [Required]
        public string DeveloperName { get; set; }
        public virtual List<Application> Applications { get; set; }
    }

public class Application 
    {
        public int Id { get; set; }
        [Required]
        public string Name { get; set; }
        [Required]
        public string Description { get; set; }
        public string Note { get; set; }
        public Developer Owner { get; set;}
        public virtual List<Developer> Developers { get; set; }
    }

protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {

            modelBuilder.Entity<Developer>()
                .HasMany<Application>(d => d.Applications)
                .WithMany(a => a.Developers)
                .Map(ad =>
                {
                    ad.MapLeftKey("DeveloperRefId");
                    ad.MapRightKey("ApplicationRefId");
                    ad.ToTable("DeveloperApplication");
                });
        }

Above describes my setup. I've tried so many things, but any time a new application is added, EF creates a new developer to associate with it.

                context.Applications.Add(app);
                   // no matter what I try here I get a duplicate developer
                context.SaveChanges();
                return Ok(app.Id);

Any suggestions would be greatly appreciated! Thank you!

Where is the Application.Developers collection? And what's the purpose of Application.Owner property, which defines another one-to-many relationship between Developer and Application? Your issue might be related to that property rather than the may-to-many relationship. — Ivan Stoev
– Ivan Stoev, Commented Feb 16, 2018 at 19:50
Sorry, I was missing the developers list on this post and have updated my question accordingly. The purpose of Application.Owner is the 1 developer who is the lead on the project. I suspect this may be indeed causing the issue? — Joseph
– Joseph, Commented Feb 16, 2018 at 19:58

henoc salinas · Accepted Answer · 2018-02-16 20:01:01Z

1

Change:

public class Application 
{
    public int Id { get; set; }
    [Required]
    public string Name { get; set; }
    [Required]
    public string Description { get; set; }
    public string Note { get; set; }
    public Developer Owner { get; set;}
}

To:

public class Application 
{
    private List<Developer> _Developers; 
    public int Id { get; set; }
    [Required]
    public string Name { get; set; }
    [Required]
    public string Description { get; set; }
    public string Note { get; set; }

    [Required(ErrorMessage="The Id Of Owner(owner as a developer) is Required")]
    public int DeveloperId { get; set; } 

    [ForeignKey("DeveloperId")]
    public virtual Developer Owner { get; set;}


    public virtual List<Developer> Developers { get{return _Developers;}} // This create Many to many

    public application(){
        _Developers= new List<Developer>();
    }
}

answered Feb 16, 2018 at 20:01

henoc salinas

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4 Comments

Joseph Over a year ago

Thanks for your reply! I've made these changes, but I am still getting duplicate developers whenever I add a new Application.

henoc salinas Over a year ago

when you create the Application, do not use owner = new Developer (), this creates a new developer and it is inserted into the database, better use DeveloperId = (developer's id) *

henoc salinas Over a year ago

example:

var app= new Application{DeveloperId=1, Name= "ExampleApp", Description= "an Example app" }; context.Applications.Add(app);                    // no matter what I try here I get a duplicate developer                 context.SaveChanges();                 return Ok(app.Id);

if on database not existe an develop with Id 1, the application dont save, but if existe this asigned to the developer with id 1

henoc salinas Over a year ago

check my previous comment

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