How to call base base method

Question

Cannot change source code class Base       public virtual void Say                 Console WriteLine  Called from Base                 Cannot change source code class Derived   Base       public override void Say                 Console WriteLine  Called from Derived             base Say             class SpecialDerived   Derived       public override void Say                 Console WriteLine  Called from Special Derived             base Say             class Program       static void Main string   args                SpecialDerived sd   new SpecialDerived            sd Say              The result is      Called from Special Derived    Called from Derived     this is not expected      Called from Base    How can I rewrite SpecialDerived class so that middle class  Derived  s method is not called   UPDATE  The reason why I want to inherit from Derived instead of Base is Derived class contains a lot of other implementations  Since I can t do base base method   here  I guess the best way is to do the following      Cannot change source code  class Derived   Base       public override void Say                 CustomSay             base Say               protected virtual void CustomSay                 Console WriteLine  Called from Derived              class SpecialDerived   Derived              public override void Say                 Console WriteLine  Called from Special Derived             base Say                      protected override void CustomSay                 Console WriteLine  Called from Special Derived

User · Answer

If you want to access to base class data you must use  this  keyword or you use this keyword as reference for class   namespace thiskeyword       class Program               static void Main string   args                        I i   new I                int res   i m1                Console WriteLine res               Console ReadLine                         public class E               new public int x   3             public class F E               new public int x   5             public class G F               new public int x   50             public class H G               new public int x   20             public class I H               new public int x   30           public int m1                            this as  lt classname  gt   will use for accessing data to base class              int z    this as I  x   base x    this as G  x    this as F  x    this as E  x     base x refer to H             return z

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There seems to be a lot of these questions surrounding inheriting a member method from a Grandparent Class  overriding it in a second Class  then calling its method again from a Grandchild Class  Why not just inherit the grandparent s members down to the grandchildren    class A       private string mystring    A           public string Method1                 return mystring           class B   A          this inherits Method1   naturally    class C   B          this inherits Method1   naturally     string newstring       A a   new A    B b   new B    C c   new C    newstring   a Method1      returns  A  newstring   b Method1      returns  A  newstring   c Method1      returns  A    Seems simple    the grandchild inherits the grandparents method here  Think about it     that s how  Object  and its members like ToString   are inherited down to all classes in C   I m thinking Microsoft has not done a good job of explaining basic inheritance  There is too much focus on polymorphism and implementation  When I dig through their documentation there are no examples of this very basic idea

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My 2c for this is to implement the functionality you require to be called in a toolkit class and call that from wherever you need      Util cs static class Util        static void DoSomething  FooBase foo            FooBase cs class FooBase       virtual void Do     Util DoSomething  this             FooDerived cs class FooDerived   FooBase       override void Do                 FooDerived2 cs class FooDerived2   FooDerived       override void Do     Util DoSomething  this          This does require some thought as to access privilege  you may need to add some internal accessor methods to facilitate the functionality

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The answer  which I know is not what you re looking for  is   class SpecialDerived   Base       public override void Say                 Console WriteLine  Called from Special Derived             base Say              The truth is  you only have direct interaction with the class you inherit from  Think of that class as a layer - providing as much or as little of it or its parent s functionality as it desires to its derived classes   EDIT   Your edit works  but I think I would use something like this   class Derived   Base       protected bool  useBaseSay   false       public override void Say                 if this  useBaseSay              base Say            else             Console WriteLine  Called from Derived              Of course  in a real implementation  you might do something more like this for extensibility and maintainability   class Derived   Base       protected enum Mode               Standard          BaseFunctionality          Verbose           etc            protected Mode Mode               get  set             public override void Say                 if this Mode    Mode BaseFunctionality              base Say            else             Console WriteLine  Called from Derived              Then  derived classes can control their parents  state appropriately

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You can t from C    From IL  this is actually supported   You can do a non-virt call to any of your parent classes    but please don t

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Why not simply cast the child class to a specific parent class and invoke the specific implementation then  This is a special case situation and a special case solution should be used  You will have to use the new keyword in the children methods though   public class SuperBase       public string Speak     return  Blah in SuperBase        public class Base   SuperBase       public new string Speak     return  Blah in Base        public class Child   Base       public new string Speak     return  Blah in Child        public partial class MainWindow   Window       public MainWindow                 InitializeComponent             Child childObj   new Child             Console WriteLine childObj Speak                 casting the child to parent first and then calling Speak           Console WriteLine  childObj as Base  Speak               Console WriteLine  childObj as SuperBase  Speak

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This is a bad programming practice  and not allowed in C   It s a bad programming practice because   The details of the grandbase are implementation details of the base  you shouldn t be relying on them  The base class is providing an abstraction overtop of the grandbase  you should be using that abstraction  not building a bypass to avoid it  To illustrate a specific example of the previous point  if allowed  this pattern would be yet another way of making code susceptible to brittle-base-class failures  Suppose C derives from B which derives from A  Code in C uses base base to call a method of A  Then the author of B realizes that they have put too much gear in class B  and a better approach is to make intermediate class B2 that derives from A  and B derives from B2  After that change  code in C is calling a method in B2  not in A  because C s author made an assumption that the implementation details of B  namely  that its direct base class is A  would never change  Many design decisions in C  are to mitigate the likelihood of various kinds of brittle base failures  the decision to make base base illegal entirely prevents this particular flavour of that failure pattern  You derived from your base because you like what it does and want to reuse and extend it  If you don t like what it does and want to work around it rather than work with it  then why did you derive from it in the first place  Derive from the grandbase yourself if that s the functionality you want to use and extend  The base might require certain invariants for security or semantic consistency purposes that are maintained by the details of how the base uses the methods of the grandbase  Allowing a derived class of the base to skip the code that maintains those invariants could put the base into an inconsistent  corrupted state

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As can be seen from previous posts  one can argue that if class functionality needs to be circumvented then something is wrong in the class architecture  That might be true  but one cannot always restructure or refactor the class structure on a large mature project  The various levels of change management might be one problem  but to keep existing functionality operating the same after refactoring is not always a trivial task  especially if time constraints apply  On a mature project it can be quite an undertaking to keep various regression tests from passing after a code restructure  there are often obscure  oddities  that show up   We had a similar problem in some cases inherited functionality should not  execute  or should perform something else   The approach we followed below  was to put the base code that need to be excluded in a separate virtual function  This function can then be overridden in the derived class and the functionality excluded or altered  In this example  Text 2  can be prevented from output in the derived class    public class Base       public virtual void Foo                 Console WriteLine  Hello from Base             public class Derived   Base       public override void Foo                 base Foo            Console WriteLine  Text 1            WriteText2Func            Console WriteLine  Text 3               protected virtual void WriteText2Func                   Console WriteLine  Text 2               public class Special   Derived       public override void WriteText2Func                   WriteText2Func will write nothing when            method Foo is called from class Special            Also it can be modified to do something else

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public class A       public int i   0      internal virtual void test                 Console WriteLine  A test             public class B   A       public new int i   1      public new void test                 Console WriteLine  B test             public class C   B       public new int i   2      public new void test                 Console WriteLine  C test -              this as A  test

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You can also make a simple function in first level derived class  to call grand base function

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Just want to add this here  since people still return to this question even after many time  Of course it s bad practice  but it s still possible  in principle  to do what author wants with   class SpecialDerived   Derived       public override void Say                 Console WriteLine  Called from Special Derived             var ptr   typeof Base  GetMethod  Say   MethodHandle GetFunctionPointer                        var baseSay    Action Activator CreateInstance typeof Action   this  ptr           baseSay

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In cases where you do not have access to the derived class source  but need all the source of the derived class besides the current method  then I would recommended you should also do a derived class and call the implementation of the derived class   Here is an example     No access to the source of the following classes public class Base        public virtual void method1    Console WriteLine  In Base       public class Derived   Base        public override void method1    Console WriteLine  In Derived          public void method2    Console WriteLine  Some important method in Derived          Here should go your classes   First do your own derived class public class MyDerived   Base                 Then derive from the derived class    and call the bass class implementation via your derived class public class specialDerived   Derived        public override void method1                     MyDerived md   new MyDerived                This is actually the base base class implementation           MyDerived method1

[c#] How to call base.base.method()?

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