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()} };
    }
}