Your JSON isn't an array of data - it's separate strings within a single class instance.
To use it as an array, you would have to create an array / List of strings, then add each property of your class to it:
public class User
{
string[] data = null;
public User(string jdata)
{
var json_serializer = new JavaScriptSerializer();
jsonDATA json_list = json_serializer.Deserialize<jsonDATA>(jdata);
List<string> strings = new List<string>();
strings.Add(json_list._luserid);
strings.Add(json_list._mymsg);
strings.Add(json_list._mypage);
...
data = strings.ToArray();
}
}