Windows phone can't save CookieContainer - windows-phone-8

Question

I apologize for my english :)
I catch cookies from server. And try to save it in order to use cookeis later.
var Settings = IsolatedStorageSettings.ApplicationSettings;
CookieContainer _Cookie = new CookieContainer()
_Cookie.Add(new Uri("http://www.portal.fa.ru/Job/SearchResultDiv"), response.Cookies);
Settings.Clear();
Settings["UserID"] = userID;
Settings["Cookie"] = _Cookie;
Settings.Save();
Ok it working. But after restart app cookie has losted. (Object has remain but cookies count = 0). I don't know.
So i try to convert from CookieContainer to array byte than save and load it when i need it.
public static byte[] ToByte(CookieContainer data)
{
byte[] CookieByte;
DataContractSerializer serializer = new DataContractSerializer(typeof(CookieContainer));
using (var memoryStream = new MemoryStream())
{
serializer.WriteObject(memoryStream, data);
CookieByte = memoryStream.ToArray();
}
return CookieByte;
}
public static CookieContainer FromByte(byte[] data)
{
CookieContainer Cookie;
DataContractSerializer serializer = new DataContractSerializer(typeof(CookieContainer));
using (var memoryStream = new MemoryStream(data))
{
Cookie = (CookieContainer)serializer.ReadObject(memoryStream);
}
return Cookie;
}
But this code did not work again. When i convert to byte and back i losing cookies (count = 0).
So what can i do?
PS write pls your code when you deal with authorization and cookies. Thx