Entity Framework and duplicates

Question

I use Entity Framework as ORM in my project. Let's suppose I use Code-First pattern and I have two models. Such as

internal class First
{        
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int  Id { get; set; }

    public string Name { get; set; }
}

internal class Second
{        
    public int  Id { get; set; }

    public First ForeignKeyEntity { get; set; }

    // other members
}

And here is code populating database:

List<Second> res = GetData();
using (var ctx = new StatisticContext())
{
    foreach (var item in res)
    {
        ctx.Seconds.Add(item);
    }
    ctx.SaveChanges();
}

As you can see each instance of class Second has instance of class First in its member ForeignKeyEntity. Obviously some instances of First can be duplicated in res. And when I run this code I get DbUpdateException in ctx.SaveChanges() with inner exception that has the following message:

Violation of PRIMARY KEY constraint 'PK_dbo.First'. 
Cannot insert duplicate key in object 'dbo.First'. 
The duplicate key value is (29459). The statement has been terminated.

I can not to insert duplicated rows but I don't want to insert duplicates, I would like to insert row only if it doesn't exist. How to solve this problem? How to insert foreign key object only if doesn'tt exist?

@Sampath Every instance of Second has an instance of First. As for database I have two tables: First and Second. And Second has a foreign key to Id in table First — Pupkin
– Pupkin, Commented Sep 19, 2016 at 14:57
@Sampath no 1 : many. GetData is some abstract method that returns List<Second> — Pupkin
– Pupkin, Commented Sep 19, 2016 at 15:37

bilpor · Accepted Answer · 2016-09-19 15:13:48Z

1

The normal way of doing things would be to do a read first with item to see if it exists. If it does then you need to use ctx.Seconds.Update(item);

If your items are already on the context, then you can check the state. it will be either State.Modified or State.Added.

Whats in GetData()

answered Sep 19, 2016 at 15:13

bilpor

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