分别选择value和text observable

我在服务器端创建模型，并使用它像ViewModel进行knockout。我的问题是绑定选择值对象{code, name}或任何想法如何使当改变代码值也改变名称，我需要选择文本和值将可观察的依赖

My Model c#

public class Model
{
    public ClientInfo ClientInfo = new ClientInfo();
    public Address Address = new Address();
    public SearchInfo SearchInfo = new SearchInfo();
}
public class ClientInfo
{
    public string firstname = "Sunnatilla";
    public string lastname = "Axakalov";      
}

public class Address
{
    public List<CodeName> countries = new List<CodeName>();
    public CodeName country = new CodeName();
    public List<CodeName> cities = new List<CodeName>();
    public CodeName city = new CodeName();
}
public class CodeName
{
    public string code = "2";
    public string name = "Russia";
    public CodeName(){}
    public CodeName(string code, string name)
    {
        this.code = code;
        this.name = name;
    }
}

public class SearchInfo
{
    public bool NewClient = true;
}

Aspx页

     <select id="address" data-bind="options: Address.countries,
                                     optionsText: 'name',
                                     optionsValue: 'code',
                                     value: Address.country.code,
                                     event: { change: Address.country.name = ko.utils.arrayFirst(Address.countries, function (country) { if (country.code === Address.country.code) return country.name }) }"></select>
    <span data-bind="text: Address.country.code"></span>
    <span data-bind="text: Address.country.name"></span>
    <script>
        $("#out").html('<%=this.model %>');
        var jsonModel = JSON.parse('<%=this.model %>');
        // jsonModel = {"ClientInfo":{"firstname":"Sunnatilla","lastname":"Axakalov"},"Address":{"countries":[{"code":"1","name":"Kazakhstan"},{"code":"2","name":"Russia"},{"code":"3","name":"China"}],"country":{"code":"2","name":"Russia"},"cities":[],"city":{"code":"2","name":"Russia"}},"SearchInfo":{"NewClient":true}}

        function ViewModel() {
            ko.mapping.fromJS(jsonModel, {}, this); // here I creatre my view model, all childs recursively observable
        }
        var viewModel = new ViewModel();
        ko.applyBindings(viewModel);
    </script>

或者在更改Address.country.code时也更改Address.country.name

  if select option value changed Address.country.code = 1   => Address.country.name = "Kazakhstan"
  if select option value changed Address.country.code = 2   => Address.country.name = "Russia"
  if select option value changed Address.country.code = 3   => Address.country.name = "China"

我需要同时更改对键/值