The following code sample shows how to delete an OpenGL rendering context when an OpenGL window is closed. It is a continuation of the scenario used in Creating a Rendering Context and Making It Current.
// a window is about to be destroyed
case WM_DESTROY:
{
// local variables
HGLRC hglrc;
HDC hdc ;
// if the thread has a current rendering context ...
if(hglrc = wglGetCurrentContext()) {
// obtain its associated device context
hdc = wglGetCurrentDC() ;
// make the rendering context not current
wglMakeCurrent(NULL, NULL) ;
// release the device context
ReleaseDC (hwnd, hdc) ;
// delete the rendering context
wglDeleteContext(hglrc);
}