Generic method with type constraints or base class parameter

Question

If I write a method accepting a parameter which derives from a BaseClass (or an interface), as far as I know there are two ways to achieve that:

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Answer 1

In this example there isn't a big difference between the two, you can access the same members inside the method and you can call it with the same derived classes. There is a runtime difference as a generic method is compiled for each type it is invoked with.

Where generics come in useful would be if you would return a value depending on T

With generics you could do the following

T MyMethod(T obj) where T : BaseClass { ... }
MyMethod(derivedInstance).derivedProperty

Without this would be an error:

BaseClass MyMethod(BaseClass obj) { ... }
MyMethod(derivedInstance).derivedProperty // error

Note Although you mention constraining to a base class, it is worth mentioning that if you constrain not to a class, but to an interface, extra boxing will occur if the implementation is by a struct in the non generic version, this can have severe performance implications.