与代码优先实体框架的一对多关系

Question

I'm trying to set up a one-to-many relationship (I think) using code-first Entity Framework.

I have a ProductListing object which can have many associated Country objects. I had thought that I had set this up correctly, but my Countries table has a reference column for ProductListing . This is a problem because although a ProductListing can have a relationship with Country , the Country object should not be aware or reliant upon the ProductListing object.

ProductListing

public class ProductListing : AuditedEntity<long>
{
    public long ProductId { get; set; }
    public Product Product { get; set; }

    public long RetailerId { get; set; }
    public Retailers.Retailer Retailer { get; set; }

    public ICollection<Countries.Country> Countries { get; set; }

    public bool IsOfficial { get; set; }

    public decimal CurrentPrice { get; set; }
    public decimal PreviousPrice { get; set; }

    public string ListingUrl { get; set; }
    public string AffiliateString { get; set; }

    public DateTime? ReleaseDate { get; set; }
    public DateTime? ShipDate { get; set; }
    public DateTime? ExpiresDate { get; set; }
}

Country

public class Country : AuditedEntity<long>
{
    [Required]
    [StringLength(ShylockConsts.MaxNameLength)]
    public virtual string Name { get; set; }

    [Required]
    [StringLength(ShylockConsts.MaxIsoLength)]
    public virtual string IsoCode { get; set; }
}

Answer 1

What you actually have is a many-to-many relationship where a Product can have many Countries, and a Country can have many Products.

To model this, you will need an intermediate joining table to hold the Countries for each Product.

Eg.

public class ProductCountry
{
    [Required]
    public virtual long ProductID { get; set; }

    [Required]
    public virtual long CountryID { get; set; }
}

Answer 2

Add a collection nav property to the Country entity as well to model a many-to-many relationship as @Steve said (but there is no need to create an entity for the junction table in the conceptual model)

public class ProductList : ...
{
    public ICollection<Country> Countries { get; set; }
}

public class Country : ...
{
    public ICollection<ProductListing> ProductListings { get; set; }
}