Question

我是Windows手机开发的新手。我有一个名为＆＃39; State＆＃39;的班级。它保留了州的名称和资本。我已经实现了INotifyPropertyChanged接口。

public class State:INotifyPropertyChanged
{
    private string _name;
    private string _capital;
    public State() { }
    public State(string name, string capital)
    {
        this.Name=name;
        this.Capital=capital;
    }
    public string Name
    {   get
        {
            return _name;
        }
        set
        { 
            _name=value;
            OnPropertyChanged(this,"Name");
            OnPropertyChanged(this, "Name");
        }
    }
    public string Capital
    {
        get
        {
            return _capital;
        }
        set
        {
            _capital = value;
            OnPropertyChanged(this, "Capital");
            OnPropertyChanged(this, "Name");
        }    
    }
    public override string ToString()
    {
        return (Name + " " + Capital );
    }

    public event PropertyChangedEventHandler PropertyChanged;  
    public void OnPropertyChanged(object sender,string Property)  
    {  
        if (PropertyChanged != null)  
        {  
            PropertyChanged(sender, new PropertyChangedEventArgs(Property));  
        }  
    }  
}

ObservableCollection维护我的状态列表。我想更新Collection中一个元素的一个属性的更改，并反映ListBox中的更改。但是没有反映出这些变化。这是我的MainPage类。我在按钮点击事件上更改了属性值。

public partial class MainPage : PhoneApplicationPage
{
    private ObservableCollection<State> MyStatelist;

    public MainPage()
    {
        InitializeComponent();
        MyStatelist = new ObservableCollection<State>();
        MyStatelist.Add(new State("State1","Capital1"));
        States.ItemsSource = MyStatelist;
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        MyStatelist[0].Name = "Abcd";
        t1.Text = MyStatelist[0].Name;
    }
}

这是我的XAML代码

<ListBox x:Name="States" Margin="0,10" ItemsSource="{Binding MyStatelist Mode=TwoWay}" ScrollViewer.VerticalScrollBarVisibility="Visible" Background="White" Foreground="Black" Height="Auto" Width="Auto"  >
    </ListBox>

无论如何，我可以通知列表框它必须更新。

非常感谢!!

Answer 1

您绑定ObservableCollection<State>两次。首先，在MainPage构造函数中创建新对象。这就足够了。在XAML ItemsSource="{Binding MyStatelist Mode=TwoWay}"中执行此操作时，会创建ObservableCollection<State>的新实例。这就是MyStatelist[0].Name = "Abcd"无效的原因，因为MyStatelist不再被设置为项目来源。只需删除XAML中的绑定即可。

还有一件事。您必须将ItemTemplate添加到ListBox并正确绑定State类的属性。这是我的榜样：

<ListBox x:Name="States" Margin="0,10" 
         Grid.Row="1"
         ScrollViewer.VerticalScrollBarVisibility="Visible" 
         Background="White" 
         Foreground="Black" 
         Height="Auto" 
         Width="Auto">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding Name}" Margin="0, 0, 12, 0"/>
                <TextBlock Text="{Binding Capital}"/>
            </StackPanel>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

Answer 2

您尚未绑定到这些属性。请改用：

<ListBox x:Name="States" Margin="0,10" ScrollViewer.VerticalScrollBarVisibility="Visible" Background="White" Foreground="Black" Height="Auto" Width="Auto"  >
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock>
                    <TextBlock.Text>
                        <MultiBinding StringFormat="{}{0} {1}">
                            <Binding Path="Name" />
                            <Binding Path="Capital" />
                        </MultiBinding>
                    </TextBlock.Text>
                </TextBlock>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>

当ObservableCollection中元素的属性发生更改时，更新ListBox项

2 个答案: