Entity Framework duplicate key issue

Question

I have an entity called Users, and an en entity called Groups.

I have a few groups confined in my database already, but no users. I am trying to add users, and configure groups for them, but I receive the following error:

Violation of PRIMARY KEY constraint 'PK_dbo.Groups'. Cannot insert duplicate key in object 'dbo.Groups'. The duplicate key value is (admins). The statement has been terminated.

Entities are defined as follows (some info stripped)

public class User{ [Key, Column(Order = 0)] public string Name {get;set;} [ForeignKey("Organization")] [Key, Column(Order = 1)] public string Organization {get;set;} public virtual Organization Org {get;set;} public virtual ICollection<Group> Groups {get;set;} } public class Group { [Key, Column(Order=0)] public string GroupName {get;set;} }

Am i missing something basic here?

Code I am using to add users:

var user = new User { Name = "NAME", Organization = "Organization Name", Org = orgObject, Groups = LIST OF GROUPS // LIST OF GROUPS is an IList<Group> object }; context.Users.Add(user); context.SaveChanges();

@appsecguy, you did have the code. When voytek edited your post he removed that part of the question. Not sure why that edit was approved. — Craig W.
– Craig W., Commented Oct 6, 2015 at 23:43
My thought is that because the List<Group> was obtained elsewhere, rather than from the db context, it is trying to re-add it when it already exists. Would that be accurate? — appsecguy
– appsecguy, Commented Oct 6, 2015 at 23:47
@appsecguy: You're correct as to the reason why it's happening. I'm trying to figure out how to fix the problem. I think part of the problem is a fundamental issue with the model. It seems like you have a many-to-many (a group can have many users and a user can belong to many groups) but the model doesn't really reflect that. And using the group name as the primary key for groups isn't a great idea either. — Craig W.
– Craig W., Commented Oct 6, 2015 at 23:49

MarcinJuraszek · Accepted Answer · 2015-10-06 23:51:25Z

My thought is that because the List was obtained elsewhere, rather than from the db context, it is trying to re-add it when it already exists. Would that be accurate?

Correct. You have to attach the items to current dbContext to make it work.

var user = new User { Name = "NAME", Organization = "Organization Name", Org = orgObject, Groups = LIST OF GROUPS // LIST OF GROUPS is an IList<Group> object }; foreach(var group in LIST OF GROUPS) context.Groups.Attach(group); context.Users.Add(user); context.SaveChanges();

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