RemoveSpecialSumbol.cs

public static string RemoveSpecialSymbols(this string mystring)
{
    JObject j = new JObject();
    j.Add(new JProperty("", mystring));
    //string s = j.First.Value<string>();

    var sr = new StringWriter();
    var jsonWriter = new JsonTextWriter(sr)
    {
        StringEscapeHandling = StringEscapeHandling.EscapeNonAscii
    };
    new JsonSerializer().Serialize(jsonWriter, j[""]);

    var newString = sr.ToString();
    var resultString = Regex.Replace(newString, "\\\"", "");

    return resultString;
}