Question 237894 in ASP.NET Question posted in
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Asp.net – The UPDATE statement conflicted with the FOREIGN KEY constraint "FK_Restaurants_Users_UserId"

I have problem with EntityFramework relationships. I want to create a relationship between User, Restaurant and Menu Item, the question is why is the Entity Framework screaming even though I have added an optional "int?" to the UserId property? After update-database command I get an error "The UPDATE statement conflicted with the FOREIGN KEY constraint "FK_Restaurants_Users_UserId".. Cannot insert the value NULL into column ‘UserId’, table ‘FoodHost.dbo.Restaurants’; column does not allow nulls."

public class Restaurant
{
    public int Id { get; set; }
    public string Name { get; set; } = string.Empty;
    public int? UserId { get; set; }
    public User User { get; set; }
    public List<MenuItem> MenuItems { get; set; } = new List<MenuItem>();
}

public class User
{
    public int Id { get; set; }
    public string UserName { get; set; } = string.Empty;
    public List<Restaurant> Restaurants { get; set; } = new();
}

 public class MenuItem
{
    public int Id { get; set; }
    public string Name { get; set; } = string.Empty;
    public int? RestaurantId { get; set; }
    public Restaurant Restaurant { get; set; }
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<User>()
            .HasMany(u => u.Restaurants)
            .WithOne(r => r.User)
            .HasForeignKey(r => r.UserId)
            .OnDelete(DeleteBehavior.NoAction);

        modelBuilder.Entity<Restaurant>()
            .HasMany(r => r.MenuItems)
            .WithOne(mi => mi.Restaurant)
            .HasForeignKey(mi => mi.RestaurantId)
            .OnDelete(DeleteBehavior.NoAction);
    }
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2

Answers


  1. 0

    Cannot insert the value NULL into column ‘UserId’, table ‘FoodHost.dbo.Restaurants’; column does not allow nulls."

    That’s clearly telling you that Restraunts.UserId does not allow nulls. So your model and your database don’t match.

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  2. 0

    Consider using a many-to-many join table for Users of Restaurants:

    public class Restaurant
{
    public int Id { get; set; }
    public string Name { get; set; } = string.Empty;
    public List<MenuItem> MenuItems { get; set; } = new List<MenuItem>();
}
public class MenuItem
{
    public int Id { get; set; }
    public string Name { get; set; } = string.Empty;
}
public class User
{
    public int Id { get; set; }
    public string UserName { get; set; } = string.Empty;
    public List<Restaurant> Restaurants { get; set; } = new();
}
public class RestaurantUser
{
    public int RestaurantId { get; set; }
    public int UserId { get; set; }
    public List<Restaurant> Restaurants { get; set; } = new();
    public List<User> Users { get; set; } = new();
}
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