delegates - C++/CLI managed class member callback by managed code -

i designing class in c++/clr uses callback function provided user code.

this works nicely if callback function free ( i.e. not member of class ). same in pure c++.

here sample code works well:

ref class classthatusescallback { public:     typedef void (*callback_t)( string^ );     void setcallback( callback_t pfun )     {         mycallback = pfun;     }     void run()     {         if( mycallback != nullptr ) {             mycallback("this test");         }     } private:     callback_t mycallback; };  void freefunction( string^ s ) {     console::writeline( "free function callback " + s ); }  int main(array<system::string ^> ^args) {    classthatusescallback^ theclassthatusescallback        = gcnew classthatusescallback();     theclassthatusescallback->setcallback( freefunction );     theclassthatusescallback->run(); } 

however, callbacked function member of class in user code ( can make use of , change attributes of user code class )

the following code not compile

ref class classthatprovidescallback { public:     void memberfunction( string^ s )     {         console::writeline( "member function callback " + s );     }     void run()     {         classthatusescallback^ theclassthatusescallback             = gcnew classthatusescallback();         theclassthatusescallback->setcallback(              &classthatprovidescallback::memberfunction );         theclassthatusescallback->run();     }  }; 

i error

error c3374: can't take address of 'classthatprovidescallback::memberfunction' unless creating delegate instance 

when research this, find numerous explanations of how call un-managed code managed code ( , vice-versa ) not need - code involved managed. hoping can point me simple way this.

this full solution:

ref class classthatusescallback { public:     void setcallback( action<string^>^ callback )     {         mycallback = callback;     }     void run()     {         if( mycallback != nullptr ) {             mycallback("this test");         }     } private:     action<string^>^ mycallback; };  ref class classthatprovidescallback { public:     void memberfunction( string^ s )     {         console::writeline( "member function callback " + s );     }     void run()     {         classthatusescallback^ theclassthatusescallback             = gcnew classthatusescallback();         theclassthatusescallback->setcallback(gcnew action<string^>(this,             &classthatprovidescallback::memberfunction));         theclassthatusescallback->run();     }  };  int main(array<system::string ^> ^args) {     classthatprovidescallback^ c = gcnew classthatprovidescallback();     c->run();      return 0; } 

native c++ style typedef replaced .net action delegate. additional parameter this added setcallback call, required define class instance contains callback function.