private static void OnRequestHandleClosing(WinHttpRequestState state)
{
Debug.Assert(state != null, "OnRequestSendRequestComplete: state is null");
// This is the last notification callback that WinHTTP will send. Therefore, we can
// now explicitly dispose the state object which will free its corresponding GCHandle.
// This will then allow the state object to be garbage collected.
state.Dispose();
}