void ngIf=(bool newCondition)

Whether the content of the directive should be visible.

Source 

set ngIf(bool newCondition) {
  // Legacy support for cases where `null` is still passed to NgIf.
  newCondition = newCondition == true;
  if (identical(newCondition, _prevCondition)) return;
  if (newCondition) {
    _viewContainer.createEmbeddedView(_templateRef);
  } else {
    _viewContainer.clear();
  }
  _prevCondition = newCondition;
}