C#•3y ago

❔ Covariance and Contravariance C#

So I stumbled on this topic and I dont seem to grasp it properly, though I saw the following example somewhere:

class Base
{
  void func() { ... }
}
class Derived : Base
{
  void fuc() { ... }
}

Base a = new Base(); // obv fine
Base b = new Derived(); // obv fine

class Base
{
  void func() { ... }
}
class Derived : Base
{
  void fuc() { ... }
}

Base a = new Base(); // obv fine
Base b = new Derived(); // obv fine

class Base
{
  void func() { ... }
}
class Derived : Base
{
  void fuc() { ... }
}

Base a = new Base(); // obv fine
Base b = new Derived(); // obv fine

class Base
{
  void func() { ... }
}
class Derived : Base
{
  void fuc() { ... }
}

Base a = new Base(); // obv fine
Base b = new Derived(); // obv fine

Both now can call

func()

func()

func()

func(), but

b

b cannot call

fuc()

fuc()

fuc()

fuc() too as its treated as a

Base

Base

Base

Base (reference) type. Now in C++, you'd just cast

b

b to

Derived

Derived

Derived

Derived and it'd work and be perfectly valid code. The sources I looked at, mentioned that this is why covariance/contravariance exists?

❔ Covariance and Contravariance C#

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