Accessing WIN32 API functions from C++ CLI

First, add the following declaration to stdafx.h:

// TODO: reference additional headers your program requires here

#include "windows.h"

For example, when calling SendMessage, take note of the double colon at the beginning:

::SendMessage((HWND)this->button1->Handle.ToInt32(), WM_LBUTTONDOWN, 0, 0);

The following would not work:

SendMessage((HWND)this->button1->Handle.ToInt32(), WM_LBUTTONDOWN, 0, 0);

and result in the following error:

error C2661: 'System::Windows::Forms::Control::SendMessage' : no overloaded function takes 4 arguments

If the error still persists, check Project Properties->Linker->Input->Additional dependencies. Click the button with the dots and turn on the checkbox for "Inherit from parent…"