Accessing Existing db context property

Question

I've tried to solve this fro quite some time already with no luck, guessing it will be a doddle for someone with experience. I'm using the MvcMusicStore.

I have a db context and I have added a new album with a new Genre. If I want to add another album with the same Genre, how do I assign the existing Genre to the new album? As in the second album below. Thanks in advance for any help.

protected override void Seed(Models.MusicStoreDBContext context)
        {
            context.Artists.Add(new Models.Artist { Name = "Al Di Meola" });
            context.Genres.Add(new Models.Genre { Name = "Jazz" });
            context.Albums.Add(new Models.Album
            {
                Artist = new Models.Artist { Name = "Sublime" },
                Genre = new Models.Genre { Name = "Rock" },
                Price = 11.99m,
                Title = "40oz to Freedom"
            });
            context.Albums.Add(new Models.Album
            {
                Artist = new Models.Artist { Name = "Jawbox" },
                Genre = "Rock", // HOW DO I ASSIGN THIS?
                Price = 10.99m,
                Title = "For your own special sweetheart"
            });

Raphaël Althaus · Accepted Answer · 2013-07-26 11:18:55Z

1

just use a variable ?

var rock = new Models.Genre{Name="Rock"};
 context.Genres.Add(rock);
 context.Albums.Add(new Models.Album
 {
     Artist = new Models.Artist { Name = "Sublime" },
     Genre = rock,
     Price = 11.99m,
     Title = "40oz to Freedom"
 });
 context.Albums.Add(new Models.Album
 {
     Artist = new Models.Artist { Name = "Jawbox" },
     Genre = rock
     Price = 10.99m,
     Title = "For your own special sweetheart"
 });

answered Jul 26, 2013 at 11:18

Raphaël Althaus

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Comments

Ron Deijkers · Accepted Answer · 2013-07-26 11:20:48Z

0

Just assign your new Genre to a variable and then set the property to that variable.

var rockGenre = new Models.Genre() { Name = "Rock" };
context.Genres.Add(rockGenre);

context.Albums.Add(new Models.Album
            {
                Artist = new Models.Artist { Name = "Sublime" },
                Genre = rockGenre,
                Price = 11.99m,
                Title = "40oz to Freedom"
            });
            context.Albums.Add(new Models.Album
            {
                Artist = new Models.Artist { Name = "Jawbox" },
                Genre = rockGenre,
                Price = 10.99m,
                Title = "For your own special sweetheart"
            });

answered Jul 26, 2013 at 11:20

Ron Deijkers

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1 Comment

Julian Rosebury Over a year ago

Thanks for the answer. I tried it 2 ways as above. This approach worked . I did try the direct access approach first (context.Genres.FirstOrDefault(x=>x.Name=="Rock")) but got an error.

Lotok · Accepted Answer · 2013-07-26 11:35:10Z

0

Or SubQuery?

protected override void Seed(Models.MusicStoreDBContext context)
    {
        context.Artists.Add(new Models.Artist { Name = "Al Di Meola" });
        context.Genres.Add(new Models.Genre { Name = "Jazz" });
        context.Albums.Add(new Models.Album
        {
            Artist = new Models.Artist { Name = "Sublime" },
            Genre = new Models.Genre { Name = "Rock" },
            Price = 11.99m,
            Title = "40oz to Freedom"
        });
        context.Albums.Add(new Models.Album
        {
            Artist = new Models.Artist { Name = "Jawbox" },
            Genre = (context.Genres.FirstOrDefault(x=>x.Name=="Rock")),
            Price = 10.99m,
            Title = "For your own special sweetheart"
        });

    }

answered Jul 26, 2013 at 11:35

Lotok

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5 Comments

Julian Rosebury Over a year ago

Cheers buddy, this is the first solution I tried as I thought it was the cleanest, however I get the error... "Unable to determine the principal end of the 'MvcMusicStore.Models.Genre_Albums' relationship. Multiple added entities may have the same primary key." What am I missing?

Lotok Over a year ago

Sounds like a relationship issue with you database. Does album not have a 1:1 relationship with genre?

Julian Rosebury Over a year ago

Many albums to one genre, if that makes sense? Using entity framework and this is MusicStoreDbInitializer, putting initial values in the database.

Lotok Over a year ago

That makes perfect sense, can you check that relationship isn't many to many by accident, it seems concerned there will be a PK constraint breach

Julian Rosebury Over a year ago

There is a FK for Genre in Albums but not the reverse.

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