XmlDocument x = JsonConvert.DeserializeXmlNode(jsonstr);

{"users":[{"id":1,"name":"Ivan","email":"iii@mail.ru"},{"id":2,"name":"Peter","email":"ppp@mail.ru"},{"id":3,"name":"Victor","email":"vvv@mail.ru"},{"id":4,"name":"Alexander","email":"aaa@mail.ru"},{"id":5,"name":"Michael","email":"mmm@mail.ru"}]}

public class User
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }
}
public class Root
{
    public List Users { get; set; }
}

var users = Newtonsoft.Json.JsonConvert.DeserializeObject(jsonStr);

public static string SerializeToString<T>(T obj)
{
    System.Xml.Serialization.XmlSerializer serializer = new System.Xml.Serialization.XmlSerializer(typeof(T));

    using (var sw = new StringWriter())
    using (System.Xml.XmlWriter writer = System.Xml.XmlWriter.Create(sw))
    {
        serializer.Serialize(writer, obj);
        return sw.ToString();
    }
}

public void StackOverflow()
{
    var jsonStr = "{"users":[{"id":1,"name":"Ivan","email":"iii @mail.ru"},{"id":2,"name":"Peter","email":"ppp @mail.ru"},{"id":3,"name":"Victor","email":"vvv @mail.ru"},{"id":4,"name":"Alexander","email":"aaa @mail.ru"},{"id":5,"name":"Michael","email":"mmm @mail.ru"}]}";
    var users = Newtonsoft.Json.JsonConvert.DeserializeObject(jsonStr);
    var xmlStr = SerializeToString(users);
}