1. DEV331 Visual C++: Using The.NET Framework In Win32/MFC Applications Kate Gregory Gregory Consulting Limited

2. Timeline First release: Visual C++.NET 2002 New reserved keywords: __gc etc Interop Limited designer support Current release: Visual C++.NET 2003 Still great interop WinForms designer Amazing conformance to standard C++ Goodies for unmanaged C++ devs Next release: Visual C++ 2005 codename Whidbey Language changes More to follow Longhorn, Avalon, WinFX, Indigo...

3. The problem Existing code is too valuable to throw away No-one wants to be left behind as functionality advances So many things are different between MFC and WinForms Popular data types Event handling Lifetime management Global and static scope

4. Why Stay In C++? I like it TemplatesDestructorsSyntax I want the highest-performing interop I want to combine managed and unmanaged code I’m a control freak Switching languages is confusing

5. Options Call your old library from a new WinForm app Usually requires refactoring Call new.NET code from your MFC business layer From unmanaged: interop Or compile parts as managed Add a WinForm to your MFC UI Host the CLR All about placing the boundary

6. Refactoring Easiest MFC apps to move to the new world have separate presentation and logic Business layer, data layer Pass business objects (Employee) between layers rather than CRecordset or other library-specific types Converting your application to a more modular one is often the first step in porting

7. Refactoring New MFC UI New Business Layer New Data Layer Old monolithic app New WinForm UI New Web Services...

8. Calling The Business Layer The business layer is an ordinary “classic” C++ class library Unmanaged Preferably not using MFC Call it: #include the header file and linking to the.lib Just the same from managed C++ or unmanaged C++ Much easier from C++ than other managed languages

9. Calling.NET Code From MFC Code If your MFC code is compiled with /CLR, it can access any.NET objects trivially This is the big C++ advantage

10. Calling.NET Code From MFC Code Create COM-Callable Wrapper around the.NET Objects Strong name RegasmGacutiltlbexp Unmanaged code calls them as though they were COM Components #import the tlb

11. Options Call your old library from a new WinForm app Usually requires refactoring Call new.NET code from your MFC business layer From unmanaged: interop Or compile parts as managed Add a WinForm to your MFC UI Host the CLR All about placing the boundary

12. WinForm In An MFC View

13. MFC App is compiled with /clr Not the only choice, but a simple option WinForm is accessed as a managed object but also wrapped in a COleControlSite MFC View creates instance of WinForm, gets an IUnknown from it, and gets it onto the view Use gcroot<>, CCOMPtr<>, and other managed-unmanaged helpers Calling methods of the managed object is easy

14. TestMFCFormView.h The managed object: gcroot pWrappedControl; Helper class from ManagedControlHelpers CWinFormsControlWnd m_usercontrol; Ordinary click handler: afx_msg void OnBnClickedButton1();

15. OnInitialUpdate CFormView::OnInitialUpdate();ResizeParentToFit(); Controls::ControlsControl* pControl = new Controls::ControlsControl(); pWrappedControl = pControl; CComPtr spunkControl; spunkControl.Attach((IUnknown*)System::Runtime::InteropServices::Marshal::GetIUnknownForObject(pControl).ToPointer()); CWnd* pwnd = this->GetDlgItem(IDC_PLACEHOLDER); CRect rectPlaceHolder; pwnd->GetWindowRect(&rectPlaceHolder);this->ScreenToClient(rectPlaceHolder);pwnd->ShowWindow(SW_HIDE); m_usercontrol.Create(spunkControl, WS_VISIBLE | WS_TABSTOP, rectPlaceHolder, this, 0);

16. Click Handler MFC calls WinForm Very simple, use the original managed object that was wrapped: void CTestMFCFormView::OnBnClickedButton1() { UpdateData(true); pWrappedControl->LabelText = SendText; }

17. Click Handler WinForm calls MFC This is significantly harder Define a managed interface for WinForm to call Define an unmanaged interface with the same methods Have the MFC View implement the unmanaged interface Write a managed bridge class

18. Managed Interface public __gc __interface IViewLabel { __property String* get_Text(); __property String* get_Text(); __property void set_Text(String*); __property void set_Text(String*);};

19. Equivalent Unmanaged Interface class IUnmanViewLabel {public: virtual char* get_Text()=0; virtual char* get_Text()=0; virtual void set_Text(char* t)=0; virtual void set_Text(char* t)=0;};

20. Bridge Class public __gc class ViewLabelImpl: public IViewLabel { public: ViewLabelImpl(IUnmanViewLabel* v); ~ViewLabelImpl(void); __property String* get_Text(); __property void set_Text(String*); private: IUnmanViewLabel* view; };

21. Bridge Class String* ViewLabelImpl::get_Text() { return new String(view->get_Text()); return new String(view->get_Text());} void ViewLabelImpl::set_Text(String* t) { //incredibly ugly marshaling code //producing s, a char* view->set_Text(s); view->set_Text(s);}

22. Working Together

23. Options Call your old library from a new WinForm app Usually requires refactoring Call new.NET code from your MFC business layer From unmanaged: interop Or compile parts as managed Add a WinForm to your MFC UI Host the CLR All about placing the boundary

24. Hosting The CLR This is usually a last resort Unless your app is IIS, Office, SQL Server Your unmanaged code thinks it is calling COM APIs The CLR is loaded and managed code runs Take complete control of your app: when the load cost happens, how the AppDomains are managed, and so on Not for the faint of heart

25. Boundary Placement Transition cost for switching from managed to unmanaged Managed wrapper around unmanaged code will cross boundary many times For chatty calls consider adding an unmanaged wrapper with a chunky interface All the chat happens entirely in unmanaged world Similar logic when unmanaged code is calling BCL or new managed code

26. What's Next? WhidbeyLonghorn Be ready

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