Convariance, Contravariance, invariance

Convariance (covariant): a reference to a derived type can be assigned to a base class variable.

1 classAnimal2     {3          Public intNumberoflegs =4;4     }5     classDog:animal6     {7        8     }9     class ProgramTen     { One         Static voidMain () A         { -Animal A1 =NewAnimal (); -Animal A2 =NewDog ();//Assign a reference to a derived class to the base class theConsole.WriteLine ("{0}", A2. Numberoflegs); - Console.read (); -         } -}

Contravariance (contravariant): a delegate's reference to a stack variable that assigns a value to another delegate type. The constraint type of two of these delegate types is an inheritance relationship! Inverter keyword in

 classAnimal { Public intNumberoflegs =4; }    classDog:animal {}classProgram {Delegate voidaction<inchT> (T a);//In contravariant keywords        Static voidActonanimal (Animal a) {Console.WriteLine (a.numberoflegs); }        Static voidMain () {Action<Animal> Act1 = Actonanimal;//Create a delegate variable with a method parameter of type animal and assign a valueaction<dog> dog1 = Act1;//assign a variable to a delegate variable with a method parameter of type dog, where animal is the base class for dog! Dog1 (NewDog ()); }    }

Convariance, contravariance, invariance