也许这个例子可以帮助

string obj = "abcn\n\rüö&/<>";
Console.WriteLine(Serialize(obj, StringEscapeHandling.Default));
Console.WriteLine(Serialize(obj, StringEscapeHandling.EscapeHtml));
Console.WriteLine(Serialize(obj, StringEscapeHandling.EscapeNonAscii));

public static string Serialize(object o,StringEscapeHandling stringEscapeHandling)
{
    StringWriter wr = new StringWriter();
    var jsonWriter = new JsonTextWriter(wr);
    jsonWriter.StringEscapeHandling = stringEscapeHandling;
    new JsonSerializer().Serialize(jsonWriter,o);
    return wr.ToString();
}