Question

I am using EF Code First to create a database on local .\SQLEXPRESS.

Among others. I have these 2 classes:

public class Shop
{
    public int ShopID { get; set; }

    [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a name!")]
    [MaxLength(25, ErrorMessage = "Name must be 25 characters or less")]
    public string Name { get; set; }

    [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter an address!")]
    [MaxLength(30, ErrorMessage = "Address must be 30 characters or less")]
    public string Address { get; set; }

    [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a valid city name!")]
    [MaxLength(30, ErrorMessage = "City name must be 30 characters or less")]
    public string City { get; set; }

    [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a phone number!")]
    [MaxLength(14, ErrorMessage = "Phone number must be 14 characters or less")]
    public string Phone { get; set; }

    [MaxLength(100, ErrorMessage = "Description must be 50 characters or less")]
    public string Description { get; set; }

    [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a WorkTime!")]
    public DateTime WorkTimeBegin { get; set; }

    [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a WorkTime!")]
    public DateTime WorkTimeEnd { get; set; }

    public DateTime? SaturdayWorkTimeBegin { get; set; }
    public DateTime? SaturdayWorkTimeEnd { get; set; }
    public DateTime? SundayWorkTimeBegin { get; set; }
    public DateTime? SundayWorkTimeEnd { get; set; }

    public int ShoppingPlaceID { get; set; }
    public virtual ShoppingPlace ShoppingPlace { get; set; }

    public virtual ICollection<Category> Categories { get; set; }
}

public class ShoppingPlace
{
    [Key]
    public int ShopingplaceID { get; set; }

    [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a name!")]
    [MaxLength(25, ErrorMessage = "Name must be 25 characters or less")]
    public string Name { get; set; }

    [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter an address!")]
    [MaxLength(50, ErrorMessage = "Address must be 50 characters or less")]
    public string Address { get; set; }

    [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a city name!")]
    [MaxLength(30, ErrorMessage = "City must be 30 characters or less")]
    public string City { get; set; }

    [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a valid phone number!")]
    [MaxLength(14, ErrorMessage = "Phone number must be 14 characters or less")]
    public string Phone { get; set; }

    public int ShoppingCenterID { get; set; }
    public virtual ShoppingCenter ShoppingCenter { get; set; }

    public virtual ICollection<Shop> Shops { get; set; }
}

and a method in DbContext:

modelBuilder.Entity<Item>()
            .HasRequired(p => p.Category)
            .WithMany(a => a.Items)
            .HasForeignKey(a => a.CategoryID)
            .WillCascadeOnDelete(false);

        modelBuilder.Entity<Category>()
            .HasRequired(a => a.Shop)
            .WithMany(a => a.Categories)
            .HasForeignKey(a => a.ShopID)
            .WillCascadeOnDelete(false);

        modelBuilder.Entity<Shop>()
            .HasOptional(a => a.ShoppingPlace)
            .WithMany(a => a.Shops)
            .HasForeignKey(a => a.ShoppingPlaceID)
            .WillCascadeOnDelete(false);

        modelBuilder.Entity<ShoppingPlace>()
            .HasOptional(a => a.ShoppingCenter)
            .WithMany(a => a.ShoppingPlaces)
            .HasForeignKey(a => a.ShoppingCenterID)
            .WillCascadeOnDelete(false);

Why I can’t create Shop without creating and populating ShopingPlace. How to achieve that?

EDIT:

Tried with:

modelBuilder.Entity<Shop>()
            .HasOptional(a => a.ShoppingPlace)
            .WithOptionalPrincipal();

        modelBuilder.Entity<ShoppingPlace>()
            .HasOptional(a => a.ShoppingCenter)
            .WithOptionalPrincipal();

and it passed, but what is the difference? And why in SQL Server i am allowed to see
ShoppingPlaceID and ShoppingPlace_ShopingPlaceID when in the case of Item and Category i see only one?

Answer 1

Although it is hard to tell without looking at the code you are using to create the instances of the record or the exact message, it is probably because your foreign key ShoppingPlaceID is not nullable.

public int ShoppingPlaceID { get; set; } 
public virtual ShoppingPlace ShoppingPlace { get; set; } 

change

public int ShoppingPlaceID { get; set; } 

to

public int? ShoppingPlaceID { get; set; } 

you should also add the following to your OnModelCreating() routine

modelBuilder.Entity<Shop>()
    .HasOptional(m => m.ShoppingPlace)
    .WithMany(m=>m.someproperty)   // if this is not many then change this
    .HasForeignKey(m=>m.ShoppingPlaceID );