How to set a default method for an optional parameter in a method.

int getIntegerInput(Func<int, bool> condition) {
  bool valid;
  while (true) {
      Console.Write("> ");
      string input = Console.ReadLine() ?? "";
      valid = int.TryParse(input, out int value) && condition(value);
      if (valid) return value;
      else Console.WriteLine(errMsg);
  }
}

getIntegerInput((input) => { return true; });