CODEWITHSUNDEEP
c#generics
StayOnTarget
StayOnTarget

Reputation: 13058

Using the generic type parameter vs using its type constraint?

Let's say I have a class structure like this, where class Foo is a generic over a class hierarchy of Base, Derived1, etc.

abstract class Base {...}

class Derived1 : Base {...}

.
.
.

class Derivedn : Base {...}


class Foo<T> where T : Base
{
   /// XXX is a placeholder - see below
   void DoBar(XXX arg) {...}
   ...
}

Wanting DoBar() to operate on something derived from Base, does it make any difference if XXX is Base or is T ?

The constraint means that T has to be Base or one of its children; but within the scope of DoBar() it is going to treat it as an object of type Base either way -- so this seems superficially like it will make no difference. But I might be overlooking something more subtle.

Upvotes: 0

Views: 40

Answers (1)

Dusan Radovanovic
Dusan Radovanovic

Reputation: 1679

If you set xxx to Base than your method parameter can be Base or any class derived from Base. If you set xxx to T than your method parameter can be T class or any class derived from T.

So if you instantiate Foo class with the generic type of Derived1 for example, in the first case you can use Base or classes derived from Base and in the second case you can use only Derived1 or classes derived from Derived1

Upvotes: 4

Related Questions