class Beta { } class Alpha { static Beta b1; Beta b2; } public class Tester { public static void main(string[] args) { Beta b1 = new Beta(); Beta b2 = new Beta(); Alpha a1=new Alpha(); Aplha a2=new Alpha(); a1.b1=b2; a1.b2=b1; a2.b2=b2; a1=null; b1=null; b2=null; } }