// Compiler options: -r:test-anon-94-lib.dll using System; class Program { public class BaseClass { public int i; public virtual void Print () { Console.WriteLine ("BaseClass.Print"); i = 90; } } public class Derived : BaseClass { public override void Print () { Action a = () => base.Print (); a (); } } public class DerivedLibrary : BaseClassLibrary { public override void Print (int arg) { Action a = () => base.Print (30); a (); } } public static int Main () { var d = new Derived (); d.Print (); if (d.i != 90) return 1; var d2 = new DerivedLibrary (); d2.Print (0); if (d2.i != 30) return 2; return 0; } }