Question

given the following:

class A : B {}

interface I
{
 B TheObject {get;set;}
}

can I do this somehow?

class C : I
{
 public A TheObject {get;set;} 
}

note the interface has the base class and the implementation has the sub class.

Answer 1

Give this a try

class C : I
{
 public A TheObject {get;set;} 
 B I.TheObject 
 {
   get { return A; }
   set { A = value as A; }
 }
}

You may need to modify the B setter, depending on your needs. Implementing an interface this way has the following consequences. When dealing with a variable typed as a C you will not be able to access B TheObject. If you need to you will need to declare an I variable and assign it to your C var. Implementing I this way is known as an explicit implementation.

eg

C c = new C();
A a = c.TheObject; // TheObject is an A
I i = c;
B b = i.TheObject;