C＃。 EF实体sql。 如何获得具有相关对象的实体？

Question

I have made simple model for example.

public class Publisher
{
    public int Id { get; set; }

    public string Title { get; set; }

    public Address Location { get; set; }

    public virtual ICollection<Book> Books { get; set; }
}

public class Address
{
    public string Country { get; set; }
    public string City { get; set; }
    public string Street { get; set; }
    public string HouseNumber { get; set; }
}  


public class Book
{
    public int Id { get; set; }

    public string Title { get; set; }

    public string Author { get; set; }

    public int LanguageId { get; set; }

    public int? PublisherId { get; set; }
}

I need to get publishers with related books. I know how to do it using linq to entities. Is it possible to solve a problem using entity sql?

    public class CatalogContext : DbContext {...}

    public List<Publisher> GetByCity(string city)
    {
        var result = new List<Publisher>();
        string queryString;
            queryString = String.Format(@"SELECT VALUE row(a,b) 
                                        FROM CatalogContext.Publishers AS a 
                                        join CatalogContext.Books AS b on a.Id = b.PublisherId
                                        WHERE a.Location.City = '{0}'", city);
        var rows = ((IObjectContextAdapter)_context).ObjectContext.CreateQuery<DbDataRecord>(queryString).ToList();
        return ???
    }

Query returns required data but it's List<DbDataRecord> - list of pairs <publisher, book> . How to translate it to list of publishers with filled navigation property "Books"? Is it possible to write query which directly returns List<Publisher> ?

Answer 1

you can do the following:

var result = ObjectContext.Publishers.Include("Books").Include("Locations")
.Where(c => c.Location.City = "SOME_CITY").Select(c => c);

Include - basically joins the table.

Then you can drill down to books by doing the following:

var test = result[0].Books;

Why are you using direct sql command instead of Entity Framework code style?