i build these function from VB6(programming language):
Code:
void Transparent()
    {
        long test=GetWindowLong(hwnd, GWL_EXSTYLE);
        SetWindowLong( hwnd, GWL_EXSTYLE,test  | WS_EX_LAYERED);
        SetLayeredWindowAttributes (hwnd, clrBackColor, 0, LWA_COLORKEY);
        const char *text;
        text=to_string( GetLastError()).c_str();
        MessageBox(NULL,text,"erro",MB_OK);
    }
but i get an error from messagebox:
87:ERROR_INVALID_PARAMETER - The parameter is incorrect.

(these code is for hide the backcolor)
can anyone advice me?