Entity Framework Code First AddOrUpdate method insert Duplicate values

Question

I have simple entity:

public class Hall

{

    [Key]

    public int Id {get; set;}



    public string Name [get; set;}

}

Then in the

Seed

method I use

AddOrUpdate

to populate table:

var hall1 = new Hall { Name = "French" };

var hall2 = new Hall { Name = "German" };

var hall3 = new Hall { Name = "Japanese" };



context.Halls.AddOrUpdate(

    h => h.Name,

    hall1,

    hall2,

    hall3

);

Then I run in the Package Management Console:

Add-Migration Current

Update-Database

It's all fine: I have three rows in the table "Hall". But if I run in the Package Management Console

Update-Database

again I have already five rows:

Id  Name

1   French

2   Japaneese

3   German

4   French

5   Japanese

Why? I think it is should be three rows again, not five. I tried to use

Id

property instead of

Name

but it does not make the difference.

UPDATE:

This code produces the same result:

var hall1 = new Hall { Id = 1, Name = "French" };

var hall2 = new Hall { Id = 2, Name = "German" };

var hall3 = new Hall { Id = 3, Name = "Japanese" };



context.Halls.AddOrUpdate(

                h => h.Id,

                hall1);



context.Halls.AddOrUpdate(

                h => h.Id,

                hall2);



context.Halls.AddOrUpdate(

                h => h.Id,

                hall3);

Also I have the latest EntityFramework installed via nuget.

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Answer 1

Ok I was banging my face off the keyboard for an hour with this. If your table's Id field is an Identity field then it won't work so use a different one for identifierExpression. I used the Name property and also removed the Id field from the new Hall {...} initializer.

This tweak to the OPs code worked for me so I hope it helps someone:

protected override void Seed(HallContext context)
{
    context.Halls.AddOrUpdate(
        h => h.Name,   // Use Name (or some other unique field) instead of Id
        new Hall
        {
            Name = "Hall 1"
        },
        new Hall
        {
            Name = "Hall 2"
        });

    context.SaveChanges();
}

Entity Framework Code First AddOrUpdate method insert Duplicate values

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