// for String? if (myString!.trim() != "null" && myString!.trim() != "")Testing empty or null, use Dart's safe navigation if (mystring?.isEmpty ?? true) { // }String? st = ""; // print string is empty or not print(st.isEmpty); // truevar result = _contact?.email ?? ""var value = maybeSomeNumber(); if (value != null) { doSomething(); } if (myString == '' || myString == null) {