Access to a property with Interface cast - linq

Question

ActionBase, ActionA, ActionB and ActionC are Entities (from a database). ActionA, ActionB and ActionC are derived type of ActionBase.
ActionB and ActionC implements ISpecialAction with a SpecialProperty.
ex :
public interface ISpecialAction
{
Guid SpecialProperty { get; }
}
public partial class ActionBase
{
public objectX OnePropertyBase { get; set; }
}
public partial class ActionA : ActionBase
{
public objectY OnePropertyA { get; set; }
}
public partial class ActionB:ActionBase,ISpecialAction
{
public objectZ OnePropertyB { get; set; }
public Guid SpecialProperty
{
get
{
return OnePropertyB.ID;
}
}
}
public partial class ActionC : ActionBase ,ISpecialAction
{
public objectW OnePropertyC { get; set; }
public Guid SpecialProperty
{
get
{
return OnePropertyC.ID;
}
}
}
My problem is that SpecialProperty is build from other Properties of the objects (ActionB or ActionC) and when the cast (to ISpecialAction) is done, OtherProperty and OtherProperty2 are null.
I tried :
GetActionBase().ToList().Where(x=>x is ISpecialAction && ((dynamic) x).SpecialProperty== p_SpecialProperty);
GetActionBase().ToList().Where(x=>x is ISpecialAction && ((ISpecialAction) x).SpecialProperty== p_SpecialProperty);
GetActionBase().ToList().OfType<ISpecialAction>().Where(x => x.SpecialProperty== p_SpecialProperty).Cast<ActionBase>();
return GetActionOnGoing().ToList().OfType<ICityAction>().Cast<ActionBase>().Where(x => ((dynamic)x).CityId == p_CityId);
remark : OfType<> doesn't works with an Interface in Linq to entities but is ok in Linq to object
How do I access my property interface without knowing the type of the object?

Answer 1

I might missed something but this is Ok with the code you provided :
public class objectX
{
}
public class objectY
{
}
public class objectZ
{
public Guid ID { get { return Guid.NewGuid();} }
}
public class objectW
{
public Guid ID { get { return new Guid(); } }
}
class Program
{
private static Guid p_SpecialProperty;
static void Main(string[] args)
{
var result = GetActionBase().ToList().Where(x => x is ISpecialAction && ((dynamic)x).SpecialProperty == p_SpecialProperty).FirstOrDefault();
var result1 = GetActionBase().ToList().Where(x => x is ISpecialAction && ((ISpecialAction)x).SpecialProperty == p_SpecialProperty).FirstOrDefault();
var result2 = GetActionBase().ToList().OfType<ISpecialAction>().Where(x => x.SpecialProperty == p_SpecialProperty).Cast<ActionBase>().FirstOrDefault();
}
private static IEnumerable<ActionBase> GetActionBase()
{
return new List<ActionBase> {new ActionA{OnePropertyA= new objectY()}, new ActionB{OnePropertyB=new objectZ()},new ActionC{OnePropertyC=new objectW()} };
}
}

Answer 2

Not sure if I exactly understand your question, but could you try using an intermediate interface, such as:
public interface ISpecialActionB : ISpecialAction
{
objectZ OnePropertyB { get; set; }
}
public class ActionB : ActionBase, ISpecialActionB
{
//same stuff
}
and casting to that instead.
var b = new ActionB{OnePropertyB = new Whatever()};
var bAsSpecial = b as ISpecialActionB;
var whatever = b.OnePropertyB; // should not be null

Answer 3

It' ok.
Your example run very well without problem so I searched in a other way : AutoMapper.
l_List.Actions = Mapper.Map<List<ActionBase>, Action[]>(l_ActionManagement.GetActionBySpecialId(l_Special.ID).ToList());
The problem was not interfaces or Linq queries but it was that automapper need an empty constructor and in this constructor, I need to initialize OnePropertyB and OnePropertyC to compute SpecialProperty.
Thanks