using System; interface IContravariant<in T> { } interface ICovariant<out T> { } class D { public static bool Contra<T> (IContravariant<T> e1, IContravariant<T> e2) { Console.WriteLine (typeof (T)); return typeof (T) == typeof (string); } public static bool Covariant<T> (ICovariant<T> e1, ICovariant<T> e2) { Console.WriteLine (typeof (T)); return typeof (T) == typeof (object); } public static bool CovContCont<T> (ICovariant<T> e1, IContravariant<T> e2, IContravariant<T> e3) { Console.WriteLine (typeof (T)); return typeof (T) == typeof (string); } public static bool ContCovContCov<T> (IContravariant<T> e1, ICovariant<T> e2, IContravariant<T> e3, ICovariant<T> e4) { Console.WriteLine (typeof (T)); return typeof (T) == typeof (string); } public static bool CovCovCont<T> (ICovariant<T> e1, ICovariant<T> e2, IContravariant<T> e3) { Console.WriteLine (typeof (T)); return typeof (T) == typeof (string); } public static int Main () { ICovariant<object> a = null; ICovariant<string> b = null; if (!Covariant (a, b)) return 1; IContravariant<string> a_1 = null; IContravariant<object> b_1 = null; if (!Contra (a_1, b_1)) return 2; ICovariant<string> a_2 = null; IContravariant<object> b_2 = null; IContravariant<string> c_2 = null; if (!CovContCont (a_2, b_2, c_2)) return 3; IContravariant<object> a_3 = null; ICovariant<string> b_3 = null; IContravariant<string> c_3 = null; ICovariant<string> d_3 = null; if (!ContCovContCov (a_3, b_3, c_3, d_3)) return 4; Console.WriteLine ("ok"); return 0; } }