You could use an attribute on the implementation of Engine2
, like so:
[AttributeUsage(AttributeTargets.Class)]
public class HandlesGridAttribute : Attribute { }
Which you then apply to your derivation:
[HandlesGrid]
public Engine2 : EngineBase { ... }
Then, in your client, check for the attribute:
IEnumerable<EngineBase> bases = ...;
// Get all the implementations which handle the grid.
IEnumerable<EngineBase> handlesGrid = bases.
Where(b => b.GetType().
GetCustomAttributes(typeof(HandlesGridAttribute), true).Any());
// Set the active property.
foreach (EngineBase b in handlesGrid) b.Active = true;
The major drawback here (which may or may not apply to you) is that you can't change the value at runtime (since the attribute is baked in at compile time). If your engine is not dynamic in this way, then the attribute is the right way to go.
If you need to change whether or not a derivation can perform this action at runtime though, then you have to fall back to your second option, code constructs that identify what the attributes of the engine are. Mind you, it doesn't have to be a string (and I don't like that either), but it can be something that is more structured that will give you the information you're looking for.