Entity Framework Code First - Cannot insert duplicate key in object 'db'

Question

I'm using the new EF code first to one project of mine, and i'm getting a weird error, my mode is:

abstract class Member
{
   public virtual int MemberId;
  ... some other stuff

}

class User : Member
{
    public virtual string Name;
    ... some more props no new key defined
}

class MyDbContext
{
    public DbSet<User> Users {get;set;}
}

The result of the deployment to SQL Server is just ok, i've a Members Table and a Users Table (TPC). Now in my main i've the following code:

static Main()
{
   User x,y;
   using(MyDbContext ctx = new MyDbContext())
   {


    x = ctx.Users.Create();
    y = ctx.Users.Create();
    x.Name = "SomeUser";
    y.Name = "SomeUser2";
    ctx.SaveChanges();

   }
}

On save changes i get:

"Unhandled Exception: System.Data.Entity.Infrastructure.DbUpdateException: An error occurred while updating the entries. See the inner exception for de tails. ---> System.Data.UpdateException: An error occurred while updating the entries. See the inner exception for details. ---> System.Data.SqlClient .SqlException: Violation of PRIMARY KEY constraint 'PK_Users_0CF04B1821B6055D'. Cannot insert duplicate key in object 'dbo.Users'."

The MemberId by default is identity so i just not seeing what's going on here. i've tried to create the instances with new and Attach them to the context but the error was the same, any ideas? The database is empty!

Thanks.

EDIT: Forgot to told that Member is an abstract class sorry bout that.

Ryan Lundy · Accepted Answer · 2011-03-28 15:13:19Z

3

I just tested it and tables of derived types in TPC (table per concrete type) inheritance don't have PK defined as identity in EF 4.1 RC.

edited Mar 28, 2011 at 15:13

Ryan Lundy

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answered Mar 27, 2011 at 15:46

Ladislav Mrnka

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7 Comments

DVD Over a year ago

Thats true, but the Member table have an identity PK so it should do the binding automatically

Ladislav Mrnka Over a year ago

No it should not because it is table per concrete type. Each table handles its own PK. Moreover identity columns should not be used in TPC inheritance because if you query all members it will return users as well. If you do not change seeds in identity you will easily get users and members with the same id. I expect exception in that case.

DVD Over a year ago

It makes sense, the thing is that i have some common info (Member) and some other specific info (e.g User, Admin, Guest) i've mapped the member to a table because if i want to know some member name i dont need to know if it is a User or Admin, etc. The point is that an User is a Member directly so it is impossible to have the same id... Member is also an abstract class so i can't even create instances. . .

Ladislav Mrnka Over a year ago

Do you really need inheritance for this. Or better do you really need TPC inheritance? Isn't TPH enough (all members in single table and discriminator column differing type of member)?

DVD Over a year ago

No TPC was the best because 90% of time i dont need to load de User information, thats why

|

GFoley83 · Accepted Answer · 2013-05-21 07:59:37Z

1

Is MemberId autoIncremented?
Have you checked the id of your created users (with console.Writeline for exemple)?

Does it work if you do the following:

x = ctx.Users.Create();        
x.Name = "SomeUser";        
ctx.SaveChanges();        
y = ctx.Users.Create();        
y.Name = "SomeUser2";        
ctx.SaveChanges();

You should try to attach your entity before you modify it.

edited May 21, 2013 at 7:59

GFoley83

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answered Mar 27, 2011 at 15:12

Jean-Philippe Leclerc

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4 Comments

DVD Over a year ago

No it doest work, the property MemberId is identity so it should not be in the Insert Query. . . The id is always 0 that's the problem, but when I Submit the changes the EF should change the proxys MemberId automatically

Jean-Philippe Leclerc Over a year ago

You should try to attach your entity before you modify it.

DVD Over a year ago

It gives other exception with the same problem, "an object with the same key already exists"...

Jean-Philippe Leclerc Over a year ago

What happen if you set the entityKey to null before you save?

mnsr · Accepted Answer · 2014-04-17 03:48:00Z

1

I just came across this. Like the marked answer states, TPC doesn't set the key to an identity. So you can use an annotation for it:

[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }

answered Apr 17, 2014 at 3:48

mnsr

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Comments

Community · Accepted Answer · 2017-05-23 11:59:17Z

0

I also had an issue with duplicate keys. For me the reason was that I mistakenly used

Id = new Guid()

instead of

Id = Guid.NewGuid()

in a factory method for initializing my database.

This related stackoverflow question might also give some further hints: Cannot insert duplicate key in object 'dbo.User'.\r\nThe statement has been terminated

edited May 23, 2017 at 11:59

CommunityBot

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answered Jan 20, 2016 at 10:35

Stefan

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