{"response":[{"uid":1,"first_name":"Павел","last_name":"Дуров"},{"uid":2,"first_name":"Александра","last_name":"Владимирова"}]}

public class vk_user_response
{
    public List<vk_user> response { get; set; } //пользователи
    public vk_user_response()
    {
        response = new List<vk_user>();
    }
}
 
public class vk_user
{
    public int uid { get; set; } //идентификатор пользователя.
    public string first_name { get; set; } //имя.
    public string last_name { get; set; } //фамилия.
}

{"response":[2,{"uid":1,"first_name":"Павел","last_name":"Дуров"},{"uid":2,"first_name":"Александра","last_name":"Владимирова"}]}