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Marshaling Polymorphism

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Dear All,

I have trouble doing marshaling for polymorphism.

Please look at the code below:
Expand|Select|Wrap|Line Numbers
  1. //C++ code, sample.dll
  2. Class A
  3. {
  4.  
  5. }
  6.  
  7. Class B : Public A
  8. {
  9.       int i;
  10. }
  11.  
  12. void DoSomething( A *a)
  13. {
  14.  
  15. }
  16.  
  17. //Marshaling, Calling DoSomething from C#
  18. //Class A & Class B already defined in C# as well
  19. [dllimport("Sample.dll")]
  20. void DoSomething(A *a);
  21.  
  22. //use DoSomething in C#
  23. Public Use()
  24. {
  25.       //declaring class B instance
  26.       B b = new B();
  27.       b.i = 1;
  28.       DoSomething(b);
  29. }
  30.  
When i debug the code, the b.i cannot be accessed when i gone into C++ code, even if i cast the a to a b pointer.

Any idea how i can overcome this?

Thanks in advance.

Best regards,
CHOW
Dec 19 '07 #1
0 949

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