Using interfaces with Entity Framework in right way

Question

There is an DLL named DbContract that contains, inter alia, these interface (code is mostly in polish):

public interface IKategoria
{
  string Nazwa { get; set; }
  IGrupa Grupa { get; set; } 
  ICollection<IKategoriaUzytkownik> Uzytkownicy { get; set; }
  ICollection<IZdarzenie> Zdarzenia { get; set; }
}

Then I want use Entity Framework repositories in another DLL (its not a web application, just a library that knows how to save objects to a database via facede of repositories). So I’m implementing concrete classes for it:

public class Kategoria : BaseObject, IKategoria
{
    private string _Nazwa; 
    private IGrupa _Grupa; 
    private ICollection<IKategoriaUzytkownik> _Uzytkownicy;
    private ICollection<IZdarzenie> _zdarzenia;

    public string Nazwa
    {
        get { return _Nazwa; }
        set { _Nazwa = value; }
    public Guid GrupaId { get; set; }
    public virtual IGrupa Grupa
    {
        get { return _Grupa; }
        set { _Grupa = value; }
    }
    public virtual ICollection<IKategoriaUzytkownik> Uzytkownicy
    {
        get { return _Uzytkownicy; }
        set { _Uzytkownicy = value; }
    }


    public virtual ICollection<IZdarzenie> Zdarzenia
    {
        get { return _zdarzenia; }
        set { _zdarzenia = value; }
    }

}

So as you can see i need to use IKategoria, IKategoriaUzytkownicy or IZdarzenie (these are all interfaces) so I can’t use this class for Entity Framework because EF need concrete classes to save them in DB (it needs navigation properties).

So my question is: How can I deisgn my architecture so I can use interfaces in applications (web, desktop) and still be able to use Entity Framework as ORM? I don’t want to bend all my Interfaces just because of Entity Framework.

Here is very simplified UML diagram of this how it should look like. How it should be

Fendy · Accepted Answer · 2015-03-19 07:29:43Z

1

Type casting saved the hard work. Repository.Save((Kategoria)IKategoria);

If not like type casting or it is not that simple, convert that interface first into a class then save it. Please note I have long forgotten about the EF syntax though.

public void Save(IKategoria iKategoria){
    Kategoria kategoria = new IKategoriaToKategoriaConverter().Convert(iKategoria);
    Repository.Save(kategoria);
}

answered Mar 19, 2015 at 7:29

Fendy

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Comments

Bartek Wójcik · Accepted Answer · 2015-03-20 17:29:43Z

Finally i ended up with this sollution:

public partial class GrupaEF : BaseObjectEF
{


    private ICollection<KategoriaEF> _Kategorie;
    private ICollection<UzytkownikGrupaEF> _Uzytkownicy;


    public virtual ICollection<KategoriaEF> KategorieEF
    {
        get { return _Kategorie; }
        set { _Kategorie = value; }
    }
    public virtual ICollection<UzytkownikGrupaEF> UzytkownicyEF
    {
        get { return _Uzytkownicy; }
        set { _Uzytkownicy = value; }
    }


}

another file:

 public partial class GrupaEF : IGrupa
{

    public string Nazwa
    {
        get
        {
            return this.Nazwa;
        }
        set
        {
            this.Nazwa = value;

        }
    }

    public string Opis
    {
        get { return Opis; }
        set { Opis = value; }
    }
    [NotMapped]
    public ICollection<IKategoria> Kategorie
    {
        get
        {
            return (ICollection<IKategoria>)this.KategorieEF;
        }
        set { KategorieEF = (ICollection<KategoriaEF>)value; }
    }
    [NotMapped]
    public ICollection<IUzytkownikGrupa> Uzytkownicy
    {
        get { return (ICollection<IUzytkownikGrupa>)this.UzytkownicyEF; }
        set { UzytkownicyEF = (ICollection<UzytkownikGrupaEF>)value; }
    }

}

So now i can use right property in code by using not mapped properties and still let EF map whole object.

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