WPF OneWay绑定只能工作一次

问题描述 投票:0回答:1

我有一个有两个组合框的视图。一个是用户选择路由管道类型名称的地方,另一个是应该有所选管道类型的可用直径列表。

每当用户选择管道类型时,另一个组合框应更新可用直径列表。

AvailableDiameters和RoutingPipeTypeName属性在Context类中是静态的,它实现了INotifyPropertyChanged接口。在xaml中,我在这些属性中设置了绑定,在代码后面还有DataContext。

问题是,在初始化视图时,直径列表只会更新一次。

在调试时,我可以看到当管道类型名称上的选择被更改时,属性支持字段的值会正确更新,仅在UI中可用直径列表未更新...

上下文类:

public class Context : INotifyPropertyChanged
{
    public static Context This { get; set; } = new Context();
    public static string RoutingPipeTypeName
    {
        get => _routingPipeTypeName;
        set
        {
            if (_routingPipeTypeName != value)
            {
                _routingPipeTypeName = value;

               This.OnPropertyChanged(nameof(RoutingPipeTypeName));
            }
        }
    }

    public static List<double> AvailableDiameters
    {
        get => _availableDiameters;
        set
        {
            //check if new list's elements are not equal
            if (!value.All(_availableDiameters.Contains))
            {
                _availableDiameters = value;
                This.OnPropertyChanged(nameof(AvailableDiameters));
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

XAML:

<ComboBox Width="80" SelectedValue="{Binding Path=RoutingPipeTypeName, Mode=OneWayToSource}">
                    <ComboBoxItem Content="Example pipe type 1"></ComboBoxItem>
                    <ComboBoxItem Content="Example pipe type 2"></ComboBoxItem>
</ComboBox>

<ComboBox Width="80" SelectedValue="{Binding Path=RoutingDiameter, Mode=OneWayToSource}" ItemsSource="{Binding Path=AvailableDiameters, Mode=OneWay}">
                </ComboBox>

代码背后:

public Context AppContext => Context.This;

public MyView()
{
    InitializeComponent();

    Instance = this;
    DataContext = AppContext;
}

负责更新直径列表的客户端类:

public void InitializeUIContext()
{
    Context.This.PropertyChanged += UIContextChanged;

    if (Cache.CachedPipeTypes.Count > 0)
        Context.RoutingPipeTypeName = Cache.CachedPipeTypes.First().Key;
}

private void UIContextChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
    if (e.PropertyName == nameof(Context.RoutingPipeTypeName))
    {
        Context.AvailableDiameters = Cache.CachedPipeTypes.First().Value.GetAvailableDiameters();
    }
}

我希望每次在管道类型属性上更改选择时,这样的设置都会更新直径组合框。相反,它只在视图初始化时更新一次...为什么?

c# wpf data-binding
1个回答
1
投票

不要使用静态属性绑定到对象(您已正确传递给视图的DataContext)。

声明没有static修饰符的属性,并用This.OnPropertyChanged替换OnPropertyChanged

public string RoutingPipeTypeName
{
    get => _routingPipeTypeName;
    set
    {
        if (_routingPipeTypeName != value)
        {
            _routingPipeTypeName = value;
            OnPropertyChanged(nameof(RoutingPipeTypeName));
        }
    }
}

您还应该从Context类中删除static This并简单地编写

public Context AppContext { get; } = new Context();
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