C# – How to use DataContractJsonSerializer for Json

I have json structure like this:

{
   "id":"12345",
   "first_name": "dino",
   "last_name": "he",
   "emails": {
      "preferred": "1",
      "personal": "2",
      "business": "3",
      "other": "4"
   }
}

I want to get the value in Emails
So I write two class:

[DataContract]
public class UserInformation
{
    [DataMember(Name = "id")]
    public string ID { get; set; }
    [DataMember(Name = "emails")]
    public Emails emails { get; set; }
    [DataMember(Name = "last_name")]
    public string Name { get; set; }

}
[DataContract]
public class Emails
{
    [DataMember(Name = "preferred")]
    public string Preferred { get; set; }


    [DataMember(Name = "personal")]
    public string Account { get; set; }

    [DataMember(Name = "business")]
    public string Personal { get; set; }

    [DataMember(Name = "other")]
    public string Business { get; set; }
}

And
I write code like this:

StreamReader stream = new StreamReader(@"C:\Visual Studio 2012\Projects\ASP.net\WebApplication1\WebApplication2\TextFile1.txt");
string text = stream.ReadToEnd();
stream.Close();

byte[] byteArray = Encoding.UTF8.GetBytes(text);
MemoryStream stream1 = new MemoryStream(byteArray);


DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(UserInformation));
var info = serializer.ReadObject(stream1) as UserInformation;
stream1.Close();

For info, I can get other value in UserInformation, But for Emails I get nothing.
Why, And how should I write the class?
Please help me!