using System;

using System.Xml.Linq;

public class Program

{

    public static void Main()

    {

        //ok

        Console.WriteLine(new XDocument(new XElement("test","aa")).ToString());

        //System.ArgumentException: '•', hexadecimal value 0x04, is an invalid character.

        Console.WriteLine(new XDocument(new XElement("test","aa \x4")).ToString());

    }

}