AddDays method
Implementation
void AddDays(int days) {
final hr = _thisPtr.ref.vtable
.elementAt(54)
.cast<Pointer<NativeFunction<HRESULT Function(Pointer, Int32 days)>>>()
.value
.asFunction<
int Function(Pointer, int days)>()(_thisPtr.ref.lpVtbl, days);
if (FAILED(hr)) throw WindowsException(hr);
}