public static int Main(string[] args)
{
//Comments are what is printed out.
var d1 = new D1();
var d2 = new D2();
d1.Foo <C1>(); //31
Console.WriteLine();
d1.Foo <C2>(); //31
Console.WriteLine();
//d2.Foo<C1>(); //Error constraint mismatch
d2.Foo <C2>(); //421
Console.WriteLine();
B_base b_d2 = d2;
b_d2.Foo <C1>(); //1
Console.WriteLine();
b_d2.Foo <C2>(); //1
Console.WriteLine();
return(0);
}