Question

Where is it more appropriate to use

class Entity<T> {}

new Entity<User>()

as opposed to

class Entity
{
   public Entity(System.Type type) 
   {
   }
}

new Entity(typeof(User))

I realized the significance of System.Type after dealing with reflection and code generation. After a month of development and getting familiar, I look back at my choices with skepticism.

This would probably not apply to you if you do not need reflection.

Answer 1

The generic approach Entity<T> has the ability to use generic type constraints to enforce both rules and features at compile-time (i.e. T must have a public parameterless constructor and be a reference-type, for example). It doesn’t need any storage space for the type on each instance, since Entity<X> and Entity<Y> are discreet types – but as a re-statement of that: you cannot have a heterogeneous List<Entity<?>> (unless you have a common base-type) for the same reason.

It is much harder to use generics if the type is known only at run-time.