Question

My managed c++ code fails to compile with the error message

.\Window.cpp(11) : error C2440: 'initializing' : cannot convert from 'System::Windows::Forms::Form ^' to 'Enviroment::Window ^'
        No user-defined-conversion operator available, or
        Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
.\Window.cpp(11) : error C3754: delegate constructor: member function 'Enviroment::Window::_keydown' cannot be called on an instance of type 'System::Windows::Forms::Form ^'

Error   1   error C2440: 'initializing' : cannot convert from 'System::Windows::Forms::Form ^' to 'Enviroment::Window ^'    c:\Users\Thomas\Documents\Visual Studio 2008\Projects\Project_X\Project_X\Window.cpp    11
Error   2   error C3754: delegate constructor: member function 'Enviroment::Window::_keydown' cannot be called on an instance of type 'System::Windows::Forms::Form ^'  c:\Users\Thomas\Documents\Visual Studio 2008\Projects\Project_X\Project_X\Window.cpp    11

In window.h

ref class Window
    {
    public:
        Window();
        void _keydown(System::Object^ sender, System::Windows::Forms::KeyEventArgs^ e);
    }

In window.cpp

Window::Window()
    {
        Form^ form = gcnew Form();
        form->KeyDown+= gcnew KeyEventHandler(form, &Window::_keydown);
}

and later

void Window::_keydown(System::Object^ sender, System::Windows::Forms::KeyEventArgs^ e)
    {
        //stuff
    }

Help!

Answer 1

I think you mean to say:

form->KeyDown+= gcnew KeyEventHandler(this, &Window::_keydown);

In C++, a class function pointer is comprised of 2 things, the actual pointer (this part you got right) and a pointer to “this” to be passed to the function, which is of the type of the class holding the function. This is your Window, not Microsoft’s Form.