嵌套属性的数据绑定

本文关键字：数据绑定 属性 嵌套 | 更新日期: 2023-09-27 18:35:46

我对 WPF 和 XAML 很陌生，现在我被数据绑定困住了好几天！我只是想将一些嵌套属性绑定到 TextBox 和 ListView（通过 XAML），但我做错了。这是我的示例代码：

MainWindow.xaml.cs 

namespace CounterTestNestedDataBinding
{
    public partial class MainWindow : Window
    {
        public MyModel MyModel { get; set; }
        public MainWindow()
        {
            InitializeComponent();
            MyModel = new MyModel { MyCounter = new Counter() };
        }
        private void Button_Click(object sender, RoutedEventArgs e)
        {
            MyModel.MyCounter.incrementCounter();
        }
    }
}

我的模型.cs

namespace CounterTestNestedDataBinding
{
    public class MyModel : INotifyPropertyChanged
    {
        public Counter _myCounter;
        public Counter MyCounter
        {
            get { return _myCounter; }
            set
            {
                _myCounter = value;
                NotifyPropertyChanged("MyCounter");
            }
        }
        // some other members and properties ...
        public event PropertyChangedEventHandler PropertyChanged;
        private void NotifyPropertyChanged(string property)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(property));
            }
        }
    }
}

计数器.cs

namespace CounterTestNestedDataBinding
{
    public class Counter : INotifyPropertyChanged
    {
        #region Members
        private int _currentNumber;
        private ObservableCollection<int> _historyList;
        #endregion
        #region Constructor
        public Counter()
        {
            _currentNumber = 0;
            _historyList = new ObservableCollection<int>();
        }
        #endregion
        #region Properties
        public int CurrentNumber
        {
            get { return _currentNumber; }
            set
            {
                _currentNumber = value;
                NotifyPropertyChanged("CurrentNumber");
            }
        }
        public ObservableCollection<int> HistoryList
        {
            get { return _historyList; }
            set
            {
                _historyList = value;
                NotifyPropertyChanged("HistoryList");
            }
        }
        #endregion
        public void incrementCounter()
        {
            HistoryList.Add(CurrentNumber);
            CurrentNumber++;
        }
        public override string ToString()
        {
            return string.Format("CurrentNumber: {0}, HistoryList: {1}", _currentNumber, String.Join(",", _historyList));
        }
        public event PropertyChangedEventHandler PropertyChanged;
        private void NotifyPropertyChanged(string property)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(property));
            }
        }
    }
}

MainWindow.xaml

<Window x:Class="CounterTestNestedDataBinding.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:counterTestNestedDataBinding="clr-namespace:CounterTestNestedDataBinding"
        Title="MainWindow" Height="350" Width="200" ResizeMode="NoResize" WindowStartupLocation="CenterScreen"
        DataContext="{Binding RelativeSource={RelativeSource Self}}"
        >
    <StackPanel Orientation="Vertical">
        <TextBox x:Name="TextBoxCounterCurrent" Text="{Binding MyModel.MyCounter.CurrentNumber}"/>
        <Button Content="Button" Click="Button_Click"/>
        <ListView x:Name="ListViewCounterHistory" Height="75" ItemsSource="{Binding MyModel.MyCounter.HistoryList}"></ListView>
    </StackPanel>
</Window>

我的问题：

  1. 如何绑定嵌套属性？可能吗？为什么像这样的事情

    Text="{Binding MyModel.MyCounter.CurrentNumber}"

    不工作？

  2. XAML 中的"数据上下文"设置是否正确？

嵌套属性的数据绑定

在构造函数中设置数据上下文，如下所示：

public MainWindow()
{
    InitializeComponent();
    MyModel = new MyModel { MyCounter = new Counter() };
    this.DataContext = MyModel;
}

然后，当然，数据的路径会发生变化，因为您要绑定的数据位于 MyModel 下。应按如下方式更改绑定：

<StackPanel Orientation="Vertical">
    <TextBox x:Name="TextBoxCounterCurrent" Text="{Binding MyCounter.CurrentNumber}"/>
    <Button Content="Button" Click="Button_Click"/>
    <ListView x:Name="ListViewCounterHistory" Height="75" ItemsSource="{Binding MyCounter.HistoryList}"></ListView>
</StackPanel>

编辑：

这就是使用 XAML 执行此操作的方式。

<Window x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:WpfApplication1"
    xmlns:system="clr-namespace:System;assembly=mscorlib"
    Title="MainWindow" Height="350" Width="525" >
<Window.Resources>
    <local:MyModel x:Key="myModal" />
</Window.Resources>
<StackPanel Orientation="Vertical" DataContext="{StaticResource myModal}">
    <TextBox x:Name="TextBoxCounterCurrent" Text="{Binding MyCounter.CurrentNumber}"/>
    <Button Content="Button" Click="Button_Click"/>
    <ListView x:Name="ListViewCounterHistory" Height="75" ItemsSource="{Binding MyCounter.HistoryList}"></ListView>
</StackPanel>

和代码更改如下所示：

 public partial class MainWindow : Window
{
    public MyModel MyModel { get; set; }
    public MainWindow()
    {
        InitializeComponent();
        //MyModel = new MyModel { MyCounter = new Counter() };
        //this.DataContext = MyModel;
    }
    private void Button_Click(object sender, RoutedEventArgs e)
    {
        var myModel = this.Resources["myModal"] as MyModel;
        if (myModel != null)
        {
            myModel.MyCounter.incrementCounter();
        }
    }
}

顺便说一下，你应该在MyModel构造函数中初始化_myCounter。

我不

认为你的结论是完全正确的，你实际上忽略了这里真正的问题。

只需将您的属性创建为

private MyModel myModel;
    public MyModel MyModel
    {
        get { return myModel;}
        set { myModel = value;
            NotifyPropertyChanged("MyModel");
        }
    }

问题是 MyModel 属性在控件初始化后初始化，但绑定引擎如何知道它必须刷新视图，因为此属性仍然是 null，因为您尚未告诉引擎拉取绑定值。

或者只是在视图之前初始化属性的值，该值也将起作用。

public MainWindow()
    {
        MyModel = new MyModel { MyCounter = new Counter() };    
        InitializeComponent();                   
    }

因此，WPF 确实支持嵌套/点绑定。

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