c# - 查看到 ViewModel 到设置

Question

是否可以将 currentDevices 重构为一个集合？
基本上，我有三个组合框，其中 selectedvalue 绑定(bind)到 currentDevices。然后 currentDevices 取自设置文件。

看法

<ComboBox ItemsSource="{Binding availableDevices}"
          SelectedValue="{Binding currentDevice1}">
</ComboBox>
<ComboBox ItemsSource="{Binding availableDevices}"
          SelectedValue="{Binding currentDevice2}">
</ComboBox>
<ComboBox ItemsSource="{Binding availableDevices}"
          SelectedValue="{Binding currentDevice3}">
</ComboBox>

View 模型

public string currentDevice1 {
    get
    {
        return SampleSettings.Default.Device1;
    }
    set
    {
        SampleSettings.Default.Device1 = value;
    }

}
public string currentDevice2
{
    get
    {
        return SampleSettings.Default.Device2;
    }
    set
    {
        SampleSettings.Default.Device2 = value;
    }
}
public string currentDevice3
{
    get
    {
        return SampleSettings.Default.Device3;
    }
    set
    {
        SampleSettings.Default.Device3 = value;
    }
}

Answer 1

我会写一个 DeviceOptionViewModel ，并给主视图模型一个 ObservableCollection。

DeviceOptionViewModel.cs

public class DeviceOptionViewModel : INotifyPropertyChanged 
{
    public event PropertyChangedEventHandler PropertyChanged;

    private string _currentDevice;
    public String CurrentDevice {
        get { return _currentDevice; }
        set { 
            _currentDevice = value; 
            PropertyChanged?.Invoke(this, 
                new PropertyChangedEventArgs(nameof(CurrentDevice));
        }
    }

    //  Parent event assigns this to his own availableDevices
    //  when he creates this.
    public IEnumerable AvailableDevices { get; set; }
}

主虚拟机:

    public ObservableCollection<DeviceOptionViewModel> 
        CurrentDevices { get; private set; }
            = new ObservableCollection<DeviceOptionViewModel>();

XAML:

<ItemsControl
    ItemsSource="{Binding CurrentDevices}"
    >
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <!-- DataContext here is DeviceOptionViewModel. We gave it its 
                 own reference to AvailableDevices to simplify binding. -->
            <ComboBox 
                ItemsSource="{Binding AvailableDevices}"
                SelectedValue="{Binding CurrentDevice}"
                />
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

返回主视图模型:

protected void PopulateCurrentDevices(IEnumerable<String> stringsFromWherever)
{
    CurrentDevices.Clear();

    foreach (var device in stringsFromWherever)
    {
        var dovm = new DeviceOptionViewModel() {
                CurrentDevice = device,
                AvailableDevices = this.availableDevices
            };

        dovm.PropertyChanged += DeviceOptionViewModel_PropertyChangedHandler;

        CurrentDevices.Add(dovm);
    }
}

protected void DeviceOptionViewModel_PropertyChangedHandler(object sender, 
     PropertyChangedEventArgs e)
{
    var dopt = sender as DeviceOptionViewModel;

    if (e.PropertyName == nameof(DeviceOptionViewModel.CurrentDevice))
    {
        //  Do stuff
    }
}

所以你填充和重新填充 CurrentDevices根据需要在您的 View 模型中，如果所有通知都正确完成，用户界面将神奇地出现。

如果您创建一个新的 ObservableCollection并将其分配给 CurrentDevices属性(property)，你需要提高 PropertyChanged(nameof(CurrentDevices))在主视图模型上。我将 setter 设为私有(private)以避免必须实现该细节。如果不是一个庞大的集合，不妨只是 Clear()和 Add()在同一个旧实例上。