Coordination and resistance in C #

1. Using system;
2. Using system. Collections. Generic;
3. Using system. LINQ;
4. Using system. text;
6. Namespace CSHARP Basics
7. {
8. Covariant commissioned by class
9. {
10. // Return type covariant of the delegate Method
11. // Define the delegate to return the person instance
12. Public Delegate person returnmyobj ();
14. Public static void main ()
15. {
16. // Register the delegate
17. Returnmyobj MYDEL = new returnmyobj (delegated covariant. porcessmyfunc );
18. Person reobj = MYDEL ();
20. If (reobj is student)
21. {
22. Console. writeline ("the returned subclass instance ");
23. }
24. Else
25. {
26. Console. writeline ("not a subclass instance returned ");
27. }
29. Console. Readline ();
31. }
33. // According to the delegate signature, but the returned is a subclass instance
34. Public static person porcessmyfunc ()
35. {
36. Return new student ();
37. }
39. }
41. Class person
42. {
43. Public string name;
44. Public int age;
45. }
47. Class student: person
48. {
49. Public int stuid;
50. }
51. }
53. // Resistance to changes: Changes to the parent class
54. // Covariant: Changes to the subclass direction