C# 刷新ListCollectionView将ComboBox中选定项的值设置为null

我有一个带有

列表框

和两个

组合框

的视图。当我在

列表框

中选择一个项目时，

组合框

的内容/值将根据所选项目的属性值刷新。在我的场景中，

列表框

包含客户列表，第一个

组合框

包含国家列表。所选项目是客户的原产国。第二个组合框包含城市列表。所选城市是客户的始发城市

    <Grid Grid.Column="0" DataContext="{Binding SelectedClient}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="25"/>
            <RowDefinition Height="25"/>
        </Grid.RowDefinitions>

        <TextBlock Grid.Column="0" Grid.Row="0" Text="Country"/>
        <local:ComboBox Grid.Column="1" Grid.Row="0" SelectedItem="{Binding Country}"
                        Command="{Binding DataContext.CountryChangedCommand, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}"
                        ItemsSource="{Binding DataContext.Countries, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <local:ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </local:ComboBox.ItemTemplate>
        </local:ComboBox>

        <TextBlock Grid.Column="0" Grid.Row="1" Text="City"/>
        <ComboBox Grid.Column="1" Grid.Row="1" SelectedItem="{Binding City}"
                  ItemsSource="{Binding DataContext.CitiesView, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
    </Grid>

    <ListBox Grid.Column="1" ItemsSource="{Binding Models}" SelectedItem="{Binding SelectedClient}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Name}"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

第二个组合框的

ItemsSource

属性基于使用过滤器的所有城市的

observeCollection

绑定到一个

ListViewCollection

。当国家/地区

列表框中的选择更改时，我刷新过滤器以仅显示属于所选国家/地区的城市

    <Grid Grid.Column="0" DataContext="{Binding SelectedClient}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="25"/>
            <RowDefinition Height="25"/>
        </Grid.RowDefinitions>

        <TextBlock Grid.Column="0" Grid.Row="0" Text="Country"/>
        <local:ComboBox Grid.Column="1" Grid.Row="0" SelectedItem="{Binding Country}"
                        Command="{Binding DataContext.CountryChangedCommand, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}"
                        ItemsSource="{Binding DataContext.Countries, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <local:ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </local:ComboBox.ItemTemplate>
        </local:ComboBox>

        <TextBlock Grid.Column="0" Grid.Row="1" Text="City"/>
        <ComboBox Grid.Column="1" Grid.Row="1" SelectedItem="{Binding City}"
                  ItemsSource="{Binding DataContext.CitiesView, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
    </Grid>

    <ListBox Grid.Column="1" ItemsSource="{Binding Models}" SelectedItem="{Binding SelectedClient}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Name}"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

假设客户A来自新西兰奥克兰，客户B来自加拿大多伦多。当我选择A时，一切正常。第二个
组合框
仅填充新西兰城市，并选择奥克兰。现在我选择B，选择的国家现在是加拿大，城市列表只包含加拿大城市，选择多伦多。如果现在我回到A，新西兰在国家中被选中，城市列表仅包含来自新西兰的城市，但奥克兰未被选中

    <Grid Grid.Column="0" DataContext="{Binding SelectedClient}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="25"/>
            <RowDefinition Height="25"/>
        </Grid.RowDefinitions>

        <TextBlock Grid.Column="0" Grid.Row="0" Text="Country"/>
        <local:ComboBox Grid.Column="1" Grid.Row="0" SelectedItem="{Binding Country}"
                        Command="{Binding DataContext.CountryChangedCommand, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}"
                        ItemsSource="{Binding DataContext.Countries, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <local:ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </local:ComboBox.ItemTemplate>
        </local:ComboBox>

        <TextBlock Grid.Column="0" Grid.Row="1" Text="City"/>
        <ComboBox Grid.Column="1" Grid.Row="1" SelectedItem="{Binding City}"
                  ItemsSource="{Binding DataContext.CitiesView, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
    </Grid>

    <ListBox Grid.Column="1" ItemsSource="{Binding Models}" SelectedItem="{Binding SelectedClient}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Name}"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

当我调试这个场景时，我注意到当我选择B时，调用
ListCollectionView.Refresh（）
会将最初选择的客户端A上的城市值设置为
null
（在调用Refresh时放置一个断点，在模型上的城市设置器上放置另一个断点，请参见下面的代码）

    <Grid Grid.Column="0" DataContext="{Binding SelectedClient}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="25"/>
            <RowDefinition Height="25"/>
        </Grid.RowDefinitions>

        <TextBlock Grid.Column="0" Grid.Row="0" Text="Country"/>
        <local:ComboBox Grid.Column="1" Grid.Row="0" SelectedItem="{Binding Country}"
                        Command="{Binding DataContext.CountryChangedCommand, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}"
                        ItemsSource="{Binding DataContext.Countries, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <local:ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </local:ComboBox.ItemTemplate>
        </local:ComboBox>

        <TextBlock Grid.Column="0" Grid.Row="1" Text="City"/>
        <ComboBox Grid.Column="1" Grid.Row="1" SelectedItem="{Binding City}"
                  ItemsSource="{Binding DataContext.CitiesView, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
    </Grid>

    <ListBox Grid.Column="1" ItemsSource="{Binding Models}" SelectedItem="{Binding SelectedClient}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Name}"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

我猜——虽然我不是100%确定——这是因为我在城市组合框的
SelectedItem
上有一个
two-way
绑定，当过滤器将列表更新到加拿大城市时，奥克兰消失，该信息被发送回酒店，酒店随后更新为
null
。这在某种程度上是有道理的

    <Grid Grid.Column="0" DataContext="{Binding SelectedClient}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="25"/>
            <RowDefinition Height="25"/>
        </Grid.RowDefinitions>

        <TextBlock Grid.Column="0" Grid.Row="0" Text="Country"/>
        <local:ComboBox Grid.Column="1" Grid.Row="0" SelectedItem="{Binding Country}"
                        Command="{Binding DataContext.CountryChangedCommand, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}"
                        ItemsSource="{Binding DataContext.Countries, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <local:ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </local:ComboBox.ItemTemplate>
        </local:ComboBox>

        <TextBlock Grid.Column="0" Grid.Row="1" Text="City"/>
        <ComboBox Grid.Column="1" Grid.Row="1" SelectedItem="{Binding City}"
                  ItemsSource="{Binding DataContext.CitiesView, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
    </Grid>

    <ListBox Grid.Column="1" ItemsSource="{Binding Models}" SelectedItem="{Binding SelectedClient}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Name}"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

我的问题是：如何避免这种情况发生？仅刷新
ItemsSource
时，如何防止更新模型上的属性

    <Grid Grid.Column="0" DataContext="{Binding SelectedClient}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="25"/>
            <RowDefinition Height="25"/>
        </Grid.RowDefinitions>

        <TextBlock Grid.Column="0" Grid.Row="0" Text="Country"/>
        <local:ComboBox Grid.Column="1" Grid.Row="0" SelectedItem="{Binding Country}"
                        Command="{Binding DataContext.CountryChangedCommand, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}"
                        ItemsSource="{Binding DataContext.Countries, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <local:ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </local:ComboBox.ItemTemplate>
        </local:ComboBox>

        <TextBlock Grid.Column="0" Grid.Row="1" Text="City"/>
        <ComboBox Grid.Column="1" Grid.Row="1" SelectedItem="{Binding City}"
                  ItemsSource="{Binding DataContext.CitiesView, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
    </Grid>

    <ListBox Grid.Column="1" ItemsSource="{Binding Models}" SelectedItem="{Binding SelectedClient}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Name}"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

下面是我的代码（有点长，虽然我试图使其尽可能少的代码量，使问题重现）：

    <Grid Grid.Column="0" DataContext="{Binding SelectedClient}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="25"/>
            <RowDefinition Height="25"/>
        </Grid.RowDefinitions>

        <TextBlock Grid.Column="0" Grid.Row="0" Text="Country"/>
        <local:ComboBox Grid.Column="1" Grid.Row="0" SelectedItem="{Binding Country}"
                        Command="{Binding DataContext.CountryChangedCommand, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}"
                        ItemsSource="{Binding DataContext.Countries, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <local:ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </local:ComboBox.ItemTemplate>
        </local:ComboBox>

        <TextBlock Grid.Column="0" Grid.Row="1" Text="City"/>
        <ComboBox Grid.Column="1" Grid.Row="1" SelectedItem="{Binding City}"
                  ItemsSource="{Binding DataContext.CitiesView, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
    </Grid>

    <ListBox Grid.Column="1" ItemsSource="{Binding Models}" SelectedItem="{Binding SelectedClient}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Name}"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

对于这个简化的示例，我在我的
窗口的构造函数中创建并填充视图模型，如下所示：

    <Grid Grid.Column="0" DataContext="{Binding SelectedClient}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="25"/>
            <RowDefinition Height="25"/>
        </Grid.RowDefinitions>

        <TextBlock Grid.Column="0" Grid.Row="0" Text="Country"/>
        <local:ComboBox Grid.Column="1" Grid.Row="0" SelectedItem="{Binding Country}"
                        Command="{Binding DataContext.CountryChangedCommand, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}"
                        ItemsSource="{Binding DataContext.Countries, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <local:ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </local:ComboBox.ItemTemplate>
        </local:ComboBox>

        <TextBlock Grid.Column="0" Grid.Row="1" Text="City"/>
        <ComboBox Grid.Column="1" Grid.Row="1" SelectedItem="{Binding City}"
                  ItemsSource="{Binding DataContext.CitiesView, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
    </Grid>

    <ListBox Grid.Column="1" ItemsSource="{Binding Models}" SelectedItem="{Binding SelectedClient}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Name}"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

public MainWindow()
{
    InitializeComponent();

    Country canada = new Country() { Name = "Canada" };
    Country germany = new Country() { Name = "Germany" };
    Country vietnam = new Country() { Name = "Vietnam" };
    Country newZealand = new Country() { Name = "New Zealand" };

    List<City> canadianCities = new List<City>
    {
        new City { Country = canada, Name = "Montréal" },
        new City { Country = canada, Name = "Toronto" },
        new City { Country = canada, Name = "Vancouver" }
    };
    canada.Cities = canadianCities;

    List<City> germanCities = new List<City>
    {
        new City { Country = germany, Name = "Frankfurt" },
        new City { Country = germany, Name = "Hamburg" },
        new City { Country = germany, Name = "Düsseldorf" }
    };
    germany.Cities = germanCities;

    List<City> vietnameseCities = new List<City>
    {
        new City { Country = vietnam, Name = "Ho Chi Minh City" },
        new City { Country = vietnam, Name = "Da Nang" },
        new City { Country = vietnam, Name = "Hue" }
    };
    vietnam.Cities = vietnameseCities;

    List<City> newZealandCities = new List<City>
    {
        new City { Country = newZealand, Name = "Auckland" },
        new City { Country = newZealand, Name = "Christchurch" },
        new City { Country = newZealand, Name = "Invercargill" }
    };
    newZealand.Cities = newZealandCities;

    ObservableCollection<ClientModel> models = new ObservableCollection<ClientModel>
    {
        new ClientModel { Name = "Bob", Country = newZealand, City = newZealandCities[0] },
        new ClientModel { Name = "John", Country = canada, City = canadianCities[1] }
    };

    List<Country> countries = new List<Country>
    {
        canada, newZealand, vietnam, germany
    };

    List<City> cities = new List<City>();
    cities.AddRange(canadianCities);
    cities.AddRange(germanCities);
    cities.AddRange(vietnameseCities);
    cities.AddRange(newZealandCities);

    ViewModel vm = new ViewModel(models, countries, cities);

    this.DataContext = vm;
}

public主窗口（）
{
初始化组件（）；
Country canada=新国家（）{Name=“canada”}；
国家德国=新国家（{Name=“germany”}；
国家越南=新国家（{Name=“越南”}；
国家新西兰=新西兰（{Name=“新西兰”}；
列出加拿大城市=新列表
{
新城{Country=canada，Name=“Montréal”}，
新城{Country=加拿大，Name=“多伦多”}，
新城{Country=加拿大，Name=“温哥华”}
};
加拿大。城市=加拿大城市；
列表相关性=新列表
{
新城{国家=德国，Name=“法兰克福”}，
新城{国家=德国，Name=“汉堡”}，
新城{国家=德国，Name=“Düsseldorf”}
};
德国。城市=德国；
列出越南城市=新列表
{
新城{Country=越南，Name=“胡志明市”}，
新城{Country=越南，Name=“岘港”}，
新城{国家=越南，Name=“Hue”}
};
越南。城市=越南城市；
列出新西兰城市=新列表
{
新西兰城市{Country=新西兰，Name=“奥克兰”}，
新西兰城市{Country=新西兰，Name=“基督城”}，
新西兰城市{Country=新西兰，Name=“Invercargill”}
};
新西兰。城市=新西兰城市；
ObservableCollection模型=新的ObservableCollection
{
新客户端模型{Name=“Bob”，国家=新西兰，城市=新西兰城市[0]}，
新客户端模型{Name=“John”，国家=加拿大，城市=加拿大城市[1]}
};
列表国家=新列表
{
加拿大、新西兰、越南、德国
};
列表城市=新列表（）；
城市。AddRange（加拿大城市）；
城市。添加范围（德国）；
城市。AddRange（越南城市）；
cities.AddRange（新西兰城市）；
ViewModel vm=新ViewModel（模型、国家/地区、城市）；
this.DataContext=vm；
}

只需复制/粘贴上述所有代码，就可以重现问题。我正在使用.NET4.0

    <Grid Grid.Column="0" DataContext="{Binding SelectedClient}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="25"/>
            <RowDefinition Height="25"/>
        </Grid.RowDefinitions>

        <TextBlock Grid.Column="0" Grid.Row="0" Text="Country"/>
        <local:ComboBox Grid.Column="1" Grid.Row="0" SelectedItem="{Binding Country}"
                        Command="{Binding DataContext.CountryChangedCommand, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}"
                        ItemsSource="{Binding DataContext.Countries, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <local:ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </local:ComboBox.ItemTemplate>
        </local:ComboBox>

        <TextBlock Grid.Column="0" Grid.Row="1" Text="City"/>
        <ComboBox Grid.Column="1" Grid.Row="1" SelectedItem="{Binding City}"
                  ItemsSource="{Binding DataContext.CitiesView, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
    </Grid>

    <ListBox Grid.Column="1" ItemsSource="{Binding Models}" SelectedItem="{Binding SelectedClient}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Name}"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

最后，我阅读（和其他一些人）并尝试将给出的建议应用到我的案例中，但没有成功。我想我做错了事情：

    <Grid Grid.Column="0" DataContext="{Binding SelectedClient}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="25"/>
            <RowDefinition Height="25"/>
        </Grid.RowDefinitions>

        <TextBlock Grid.Column="0" Grid.Row="0" Text="Country"/>
        <local:ComboBox Grid.Column="1" Grid.Row="0" SelectedItem="{Binding Country}"
                        Command="{Binding DataContext.CountryChangedCommand, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}"
                        ItemsSource="{Binding DataContext.Countries, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <local:ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </local:ComboBox.ItemTemplate>
        </local:ComboBox>

        <TextBlock Grid.Column="0" Grid.Row="1" Text="City"/>
        <ComboBox Grid.Column="1" Grid.Row="1" SelectedItem="{Binding City}"
                  ItemsSource="{Binding DataContext.CitiesView, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
    </Grid>

    <ListBox Grid.Column="1" ItemsSource="{Binding Models}" SelectedItem="{Binding SelectedClient}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Name}"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

我也读过，但是如果我的
列表框变大了，我可能最终不得不明确地跟踪数百个项目，如果可能的话，我不想这样做。
你的模型有点多余。你们有国家的名单，每个国家都有城市的名单。然后组成城市的整体列表，在选择更改时更新。如果您将更改城市组合框的数据源，您将获得所需的行为：

    <Grid Grid.Column="0" DataContext="{Binding SelectedClient}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="25"/>
            <RowDefinition Height="25"/>
        </Grid.RowDefinitions>

        <TextBlock Grid.Column="0" Grid.Row="0" Text="Country"/>
        <local:ComboBox Grid.Column="1" Grid.Row="0" SelectedItem="{Binding Country}"
                        Command="{Binding DataContext.CountryChangedCommand, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}"
                        ItemsSource="{Binding DataContext.Countries, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <local:ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </local:ComboBox.ItemTemplate>
        </local:ComboBox>

        <TextBlock Grid.Column="0" Grid.Row="1" Text="City"/>
        <ComboBox Grid.Column="1" Grid.Row="1" SelectedItem="{Binding City}"
                  ItemsSource="{Binding DataContext.CitiesView, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
    </Grid>

    <ListBox Grid.Column="1" ItemsSource="{Binding Models}" SelectedItem="{Binding SelectedClient}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Name}"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

    <ComboBox Grid.Column="1" Grid.Row="1" SelectedItem="{Binding City}"
              ItemsSource="{Binding Country.Cities}">
        <ComboBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Name}"/>
            </DataTemplate>
        </ComboBox.ItemTemplate>
    </ComboBox>

我尝试了两种解决方案，它们都有效。我会选择第一个，它将更少的代码，更容易理解和维护。然而，我真的很想知道为什么使用UI调度程序可以帮助解决这个问题？？我没有调试代码来查看发生了什么，但据我所知，UI线程上已经运行了所有东西，我不明白为什么使用UI dispatcher会在某种程度上有所帮助……UI dispatcher的方法BeginInvoke（）将在UI线程上调度方法调用，所以当UI线程可以自由执行某些操作时，它将执行您指定的操作。因此，这里将选择SelectedClient