Question

Any idea how to initialize .NET delegate that points to method from ‘mixed’ class instance?

I have ‘mixed’ C++ class like this:

class CppMixClass { public:     CppMixClass(void){         dotNETclass->StateChanged += gcnew DotNetClass::ServiceStateEventHandler(&UpdateHealthState);     }    ~CppMixClass(void);    void UpdateState(System::Object^ sender, DotNetClass::StateEventArgs^ e){        //doSmth    } } 

DotNetClass is implemented in C#, and Method declaration is OK with delegate. This line generates error:

dotNETclass->StateChanged += gcnew DotNetClass::ServiceStateEventHandler(&UpdateHealthState); error C2276: '&' : illegal operation on bound member function expression 

Anyone have a clue about a problem? Maybe coz CppMixClass class is not a pure .NET (ref) class?

I got this to work when UpdateHealthState is static method, but I need pointer to instance method.

I tried smth like:

dotNETclass->StateChanged += gcnew DotNetClass::ServiceStateEventHandler(this, &UpdateHealthState); 

But this obviously doesn’t work coz this is not pointer (handle) to .NET (ref) class, (System::Object).

ServiceStateEventHandler is defined in C# as:

public delegate void ServiceStateEventHandler(object sender, ServiceStateEventArgs e); 

Thanx for reading this 🙂

Answer 1

I just found answer to this(of course by Nishant Sivakumar, man seems to have answers to all my C++/CLI interop related problems):

http://www.codeproject.com/KB/mcpp/CppCliSupportLib.aspx?display=Print

Answer is located in ‘msclr/event.h’ header, where macros for delegates in native classes are defined.

Nish’s code is following:

class Demo5 { msclr::auto_gcroot<FileSystemWatcher^> m_fsw; public: // Step (1) // Declare the delegate map where you map // native method to specific event handlers  BEGIN_DELEGATE_MAP(Demo5)     EVENT_DELEGATE_ENTRY(OnRenamed, Object^, RenamedEventArgs^) END_DELEGATE_MAP()  Demo5() {     m_fsw = gcnew  FileSystemWatcher('d:\\tmp');     // Step (2)     // Setup event handlers using MAKE_DELEGATE     m_fsw->Renamed += MAKE_DELEGATE(RenamedEventHandler, OnRenamed);     m_fsw->EnableRaisingEvents = true; } // Step (3) // Implement the event handler method  void OnRenamed(Object^, RenamedEventArgs^ e) {     Console::WriteLine('{0} -> {1}',e->OldName, e->Name); } };