Chris, The C# language designers didn't have much choice, the decision was made by the CLR designers (I suppose they could have been the same people though ;-)). Not sure why though, but it sort of makes sense to me (but see http://jeroen.nu/ for why I'm not necessarily happy with it ;-)).
Regards, Jeroen > -----Original Message----- > From: Moderated discussion of advanced .NET topics. > [mailto:[EMAIL PROTECTED]] On Behalf Of Chris Daly > Sent: Friday, December 13, 2002 01:48 > To: [EMAIL PROTECTED] > Subject: [ADVANCED-DOTNET] Reasons for restrictions on > protected access from subclasses? > > > Section 3.5.3 of the C# spec lays out some restrictions on accessing > protected members. I don't think that Java has the analogous > restrictions and I'm trying to figure out why they are necessary > or desired. > > Basically if an object has an instance typed as its base class > (or some class further up the inheritance chain) it cannot access > protected members of that instance. > > Here's the example from the spec: > > public class A > { > protected int x; > static void F(A a, B b) { > a.x = 1; // Ok > b.x = 1; // Ok > } > } > public class B: A > { > static void F(A a, B b) { > a.x = 1; // Error, must access through instance of B > b.x = 1; // Ok > } > } > > Suppose that the A we were passed in B.F was an instance of C > - another > subclass of A, like this: > > public class C: A > { > protected new int x; > } > > In this case we would still know which x to update (the one > in A), right? > > Can anybody explain the justification for this restriction? > > > Chris Daly > Rational Software > > You can read messages from the Advanced DOTNET archive, > unsubscribe from Advanced DOTNET, or > subscribe to other DevelopMentor lists at http://discuss.develop.com. > You can read messages from the Advanced DOTNET archive, unsubscribe from Advanced DOTNET, or subscribe to other DevelopMentor lists at http://discuss.develop.com.
