Question

我有以下xaml;

    <DataTemplate DataType="{x:Type NameSpace:Node}">
        <StackPanel Orientation="Horizontal">
            <TextBlock Text="{Binding Item.Value}"/>
            <ContentControl Content="{Binding Item}"/>
        </StackPanel>
    </DataTemplate>

    <DataTemplate DataType="{x:Type NameSpace:Item}">
        <TextBlock Text="{Binding Value}" />
    </DataTemplate>

当我使用Node模板显示Node对象时，我得到两个TextBlocks，它们都显示相同的值。到现在为止还挺好。项目更改时会发生此问题。当Node类触发INotifyPropertyChanged事件时，Node DataTemplate中的TextBlock会按预期更新，但Item DataTemplate中的TextBlock不会更新。

当Node类触发IPropertyChanged事件时，如何让Item DataTemplate更新其绑定？

更新事实证明，上述方法适用于以下简单方案;

的Xaml

        <DataTemplate DataType="{x:Type DataTemplateExample:Node}">
            <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding Item.Value}"/>
                <ContentControl Content="{Binding Item}"/>
            </StackPanel>
        </DataTemplate>

        <DataTemplate DataType="{x:Type DataTemplateExample:Item}">
            <TextBlock Text="{Binding Value}" />
        </DataTemplate>
    </Window.Resources>

    <Grid>
        <StackPanel Orientation="Vertical">
            <ContentControl Content="{Binding MyNode}"/>
            <Button Command="{Binding ChangeMyNodeItem}">Change Item</Button>
        </StackPanel>
    </Grid>
</Window>

C＃

public class MainViewModel
{
    private readonly Node myNode;
    private readonly DelegateCommand changeMyNodeItemCmd;

    public MainViewModel()
    {
        myNode = new Node {Item = new Item("a")};
        changeMyNodeItemCmd = new DelegateCommand(()=>
            myNode.Item = new Item("b"));
    }

    public Node MyNode { get { return myNode; } }

    public ICommand ChangeMyNodeItem
    {
        get { return changeMyNodeItemCmd; }
    }
}

public class Node : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private Item item;
    public Item Item
    {
        set
        {
            item = value;
            if (PropertyChanged != null)
                PropertyChanged(this,new PropertyChangedEventArgs("Item"));
        }
        get { return item; }
    }
}

public class Item
{
    private readonly string value;

    public Item(string value)
    {
        this.value = value;
    }

    public string Value
    {
        get { return value; }
    }
}

在我的真实场景中，我使用代理，我认为这是让WPF感到困惑的原因。物品实际上并没有改变 - 它被重新映射。

最终，我使用类似于ShadeOfGray提出的解决方案解决了这个问题。但我应该指出，除非你使用代理，否则没有必要这样做。

Answer 1

根据您发布的内容，我认为您正在错误的类中触发NotifyPropertyChanged。这样的事情应该在你的场景中正常工作。

根据评论更新：

public class Node : INotifyPropertyChanged
{
    private Item item;

    public event PropertyChangedEventHandler PropertyChanged;

    public Item Item
    {
        get
        {
            return item;
        }

        set
        {
            item = value;

            this.NotifyPropertyChanged("Item");

            if (item != null)
            {
                item.ForcePropertyChanged("Value");
            }
        }
    }

    protected void NotifyPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

public class Item : INotifyPropertyChanged
{
    private string itemValue;

    public Item()
    {
        this.Value = string.Empty;
    }

    public event PropertyChangedEventHandler PropertyChanged;

    public string Value
    {
        get
        {
            return itemValue;
        }

        set
        {
            itemValue = value;

            NotifyPropertyChanged("Value");
        }
    }

    public void ForcePropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    protected void NotifyPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

在DataTemplate中更新DataTemplate的绑定

1 个答案: