How to use interface properties with CodeFirst

Question

I have the following entities:

public interface IMyEntity
{
    [Key]
    int Id { get; set; }
    IMyDetail MyDetail { get; set; }
    ICollection

        

Answer 1

A workaround is to create a special implementation for each interface you want to use with Entity Framework, utilizing the adapter pattern:

Wrapper per Interface

// Entity Framework will recognize this because it is a concrete type
public class SecondLevelDomainRep: ISecondLevelDomain
{
    private readonly ISecondLevelDomain _adaptee;

    // For persisting into database
    public SecondLevelDomainRep(ISecondLevelDomain adaptee)
    {
        _adaptee = adaptee;
    }

    // For retrieving data out of database
    public SecondLevelDomainRep()
    {
        // Mapping to desired implementation
        _adaptee = new SecondLevelDomain();
    }

    public ISecondLevelDomain Adaptee
    {
        get { return _adaptee; }
    }

    public string Id
    {
        get { return _adaptee.Id; }
        set { _adaptee.Id = value; }
    }

    // ... whatever other members the interface defines
}

Saving and Loading Example

    // Repositor is your DbContext

    public void SubmitDomain(ISecondLevelDomain secondLevelDomain)
    {
         Repositor.SecondLevelDomainReps.Add(new SecondLevelDomainRep(secondLevelDomain));
         Repositor.SaveChanges();
    }

    public IList RetrieveDomains()
    {
         return Repositor.SecondLevelDomainReps.Select(i => i.Adaptee).ToList();
    }

Using Navigational Properties / Foreign Keys / Parent Child Mappings

For more complex interfaces/classes, you may get InvalidOperationException - see Conflicting changes with code first foreign key in Entity Framework for an implementation that works with such object hierarchies