基于Silverlight数据网格内另一个组合框的SelectedItem更新组合框项资源

我在一个

数据网格中有两个
组合框
。当在第一个
组合框
中进行选择时，我想更新第二个
组合框
的
项目资源
。我刚刚开始学习
Silverlight
，我正在尝试遵循
MVVM
模式。这就是我到目前为止得到的

型号

public class Country : ViewModelBase
{
    private string name;
    public string Name {...}
    public string Code { get; set; }
}
public class City : ViewModelBase
{
    private string name;
    public string Name {...}        
    public string Code { get; set; }
}
public class Location : ViewModelBase
{
    private City city;
    public City City {...}

    private Country country;
    public Country Country {...}
}

public class CountryCityViewModel : ViewModelBase
{
    private Location selectedLocation;
    public Location SelectedLocation {...}

    IRepo Repo { get; set; }
    public ObservableCollection<Location> Locations { get; set; }
    public ObservableCollection<Country> Countries { get; set; }
    public ObservableCollection<City> Cities { get; set; }       

    public CountryCityViewModel(IRepo repo)
    {
        this.Repo = repo;

        Countries = new ObservableCollection<Country>(repo.LoadCountries());
        Cities = new ObservableCollection<City>();
        Locations = new ObservableCollection<Location>(repo.LoadLocations());

        this.PropertyChanged += CountryCityViewModel_PropertyChanged;

    }

    private void UpdateCityComboBoxItemsSource(object obj)
    {
        Country selCountry = ( (Country) obj );
        if (obj != null)
        {
            UpdateCities(selCountry);
        }
    }

    void CountryCityViewModel_PropertyChanged(object sender, 
                       System.ComponentModel.PropertyChangedEventArgs e)
    {
        if (e.PropertyName == "SelectedLocation")
        {
            UpdateCities(SelectedLocation.Country);
        }
    }
    private void UpdateCities(Country country)
    {
        var newCities = Repo.LoadCities(country);
        Cities.Clear();
        foreach (var city in newCities)
        {
            Cities.Add(city);
        }
        OnPropertyChanged("Cities");
    }
}

视图模型

public class Country : ViewModelBase
{
    private string name;
    public string Name {...}
    public string Code { get; set; }
}
public class City : ViewModelBase
{
    private string name;
    public string Name {...}        
    public string Code { get; set; }
}
public class Location : ViewModelBase
{
    private City city;
    public City City {...}

    private Country country;
    public Country Country {...}
}

public class CountryCityViewModel : ViewModelBase
{
    private Location selectedLocation;
    public Location SelectedLocation {...}

    IRepo Repo { get; set; }
    public ObservableCollection<Location> Locations { get; set; }
    public ObservableCollection<Country> Countries { get; set; }
    public ObservableCollection<City> Cities { get; set; }       

    public CountryCityViewModel(IRepo repo)
    {
        this.Repo = repo;

        Countries = new ObservableCollection<Country>(repo.LoadCountries());
        Cities = new ObservableCollection<City>();
        Locations = new ObservableCollection<Location>(repo.LoadLocations());

        this.PropertyChanged += CountryCityViewModel_PropertyChanged;

    }

    private void UpdateCityComboBoxItemsSource(object obj)
    {
        Country selCountry = ( (Country) obj );
        if (obj != null)
        {
            UpdateCities(selCountry);
        }
    }

    void CountryCityViewModel_PropertyChanged(object sender, 
                       System.ComponentModel.PropertyChangedEventArgs e)
    {
        if (e.PropertyName == "SelectedLocation")
        {
            UpdateCities(SelectedLocation.Country);
        }
    }
    private void UpdateCities(Country country)
    {
        var newCities = Repo.LoadCities(country);
        Cities.Clear();
        foreach (var city in newCities)
        {
            Cities.Add(city);
        }
        OnPropertyChanged("Cities");
    }
}

和xaml

<ComboBox x:Name="CountryComboBox"
    ItemsSource="{Binding Path=DataContext.Countries,
        RelativeSource={RelativeSource AncestorType=Custom:CustomDataGrid}}"
    SelectedItem="{Binding Path=Country, Mode=TwoWay}"
    DisplayMemberPath="Name">
    <i:Interaction.Triggers>
      <i:EventTrigger EventName="SelectionChanged">
        <i:InvokeCommandAction Command="{Binding
          Path=DataContext.CountryComboBoxItemSelectedCommand,
          RelativeSource={RelativeSource AncestorType=Custom:CustomDataGrid}}"
          CommandParameter="{Binding SelectedItem,ElementName=CountryComboBox}"/>
      </i:EventTrigger>
    </i:Interaction.Triggers>
</ComboBox>

我已经做过很多次了

我以前做的是在XAML中为Country组合框创建SelectedItem属性

假设SelectedItem属性的名称为“SelectedCountry”。现在转到该属性的Setter，并将Itemsource分配给MVVM中的城市组合框

private Country _SelectedCountry;
        public Country SelectedCountry
        {
            get
            {
                return _SelectedCountry;
            }
            set
            {
                if (_SelectedCountry!= value)
                {
                    _SelectedCountry= value;

                    AllCities = get this from your datasource.
                    RaisePropertyChanged("SelectedCountry");
                }
            }

        }

希望这对你有帮助

快乐学习
 ItemsSource应该如何更改？换成什么？我只能在你的代码中看到一个城市代码列表，那么你想实现什么呢？再次将该列表换成完全相同的列表？或者您想更改Address对象中的城市代码以匹配城市名称吗？@Martin我的问题可能没有最好的例子。我更新了一个更好的问题。我要寻找的是，当用户从
Country组合框
中选择
Country
时，我想用与所选
国家相关的
城市
对象集合更新
城市组合框
的可用选项。