Covariance and contravariance of interfaces

Source: Internet
Author: User

 classAnimal { Public stringName;}//base class    classDog:animal {}//Derived Classes    Interfaceimyif< outT>//covariance keyword out, generic interface + interface covariant{T getfirst ();//Constraint Method    }    classSimplereturn<t>: imyif<t>//generic types that implement generic interfaces    {         Publict[] Items =Newt[2];//initializing an array of objects         PublicT GetFirst () {returnitems[0]; }//returns the first object of an array of objects    }    classProgram {Static voidDoSomething (imyif<animal> Returner)//static method, the method parameter is the interface of the parameter constraint to the animal object{Console.WriteLine (returner). GetFirst ().        Name); }        Static voidMain () {Simplereturn<Dog> Dogreturner =NewSimplereturn<dog> ();//instantiating an object constrained to a dog typedogreturner.items[0] =NewDog () {name="Avonlea"}//Assign Valueimyif<animal> Animalreturner = Dogreturner;//Associationbecomes an interface constrained to a animal objectDoSomething (Dogreturner);//executing a static method        }    }

Covariance and contravariance of interfaces

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