public override void Edit() { string expression = _sumUpList.Replace(SourceData, "${top}+${bottom}"); expression = _sumUpList.Replace(expression, "${top}+${bottom}"); try { string answer = EvaluateExpression(expression); if (ParameterList[0].GetValueOrDefault().Equals("answer", StringComparison.CurrentCultureIgnoreCase)) { SourceData = answer; } else if (SourceData.Contains("\n")) { SourceData = String.Concat(SourceData, "\n", answer); } else if (SourceData.Contains("=")) { SourceData = String.Concat(SourceData, answer); } else { SourceData = String.Concat(SourceData, "=", answer); } } catch (Exception mathErr) { RespondToExe("Error: " + mathErr.Message); } }