static void CovarianceDemo1()
{
var ls = new List <Sub>();
var lb = new List <Base>();
var b = new Base();
var s = new Sub();
ls.Add(s);
lb.Add(b);
// ls.Add(b); error
lb.Add(s);
DoSomething(ls);
// DoSomething2(ls); error
var fooin = new FooIn <Sub>();
var fooout = new FooOut <Sub>();
IFooIn <Sub> returnValueIn = GetFooIn();
//IFooOut<Sub> returnValueOut = GetFooOut();
// GetFooIn(fooin); illeagal due to covariance rules
GetFooOut(fooout); // legal due to covariance rules
}
static void CovarianceDemo2()
{
// In-variant
//IFoo<Base> ifbase = new Foo<Sub>();
//IFoo<Sub> ifsub = new Foo<Base>();
// Co-variance
IFooOut <Base> ifbase = new FooOut <Sub>();
//IFooOut<Sub> ifsub = new FooOut<Base>();
// Contra-variance
//IFooIn<Base> infbase = new FooIn<Sub>();
IFooIn <Sub> infsub = new FooIn <Base>();
IEnumerable <int> listInt = new List <int> {
1, 2, 3
};
IEnumerable <object> someObjects = (IEnumerable <object>)listInt;
Func <Base, Sub> func = n => new Sub();
Action <int> action = n => Console.WriteLine(n);
GetFunc(func);
}
