如果其他类对象的属性发生了变化，Gui不会更新

Question

我想将自定义类（FooClass.FooString）的某些属性（FooClass）绑定到我的MainWindow。现在，如果将一些数据绑定到gui，则下面（工作已知行为）是默认的工作解决方案。

我想要做的是在第二个代码块中（不工作，但需要的行为）。公开另一个properties对象class对象to the gui and update it. **Problem**: The TestString is not getting updated (on the gui, code behind works). The PropertyChanged 事件is also null`（未订阅？！）。

这是如何绑定数据的错误方法吗？

如果我将完整的FooClass object绑定到gui并将Path（TextBlock）设置为Foo.FooString，则gui和{{1} }已更新。但我不想这样做。

这是如何解决的？

工作已知行为

string

MainWindow.xaml

public partial class MainWindow : Window
{
    public FooClass Foo { get; } = new FooClass();

    public MainWindow()
    {
        DataContext = this;
        InitializeComponent();

        Loaded += _OnLoaded;
    }

    private async void _OnLoaded(object sender, RoutedEventArgs e)
    {
        await Task.Delay(1000);
        Foo.ChangeTheProperty();
    }
}

public class FooClass : INotifyPropertyChanged
{
    public string FooString
    {
        get => _FooString;
        set
        {
            if (_FooString == value) return;
            _FooString = value;
            OnPropertyChanged();
        }
    }
    private string _FooString = "empty";

    public void ChangeTheProperty()
    {
        FooString = "Loaded";
    }

    // ##############################################################################################################################
    // PropertyChanged
    // ##############################################################################################################################

    #region PropertyChanged

    /// <summary>
    /// The PropertyChanged Eventhandler
    /// </summary>
    public event PropertyChangedEventHandler PropertyChanged;

    /// <summary>
    /// Raise/invoke the propertyChanged event!
    /// </summary>
    /// <param name="propertyName"></param>        
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    #endregion
}

不起作用，但需要行为

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        d:DataContext="{d:DesignInstance local:MainWindow}"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <TextBlock Text="{Binding Path=Foo.FooString}" VerticalAlignment="Center" HorizontalAlignment="Center"/>
    </Grid>
</Window>

MainWindow.xaml

public partial class MainWindow : Window
{
    public string TestString => _Foo.FooString;


    private readonly FooClass _Foo;

    public MainWindow()
    {
        _Foo = new FooClass();
        DataContext = this;
        InitializeComponent();

        Loaded += _OnLoaded;
    }

    private async void _OnLoaded(object sender, RoutedEventArgs e)
    {
        await Task.Delay(1000);
        _Foo.ChangeTheProperty();
    }
}

public class FooClass : INotifyPropertyChanged
{
    public string FooString
    {
        get => _FooString;
        set
        {
            if (_FooString == value) return;
            _FooString = value;
            OnPropertyChanged();
        }
    }
    private string _FooString = "empty";

    public void ChangeTheProperty()
    {
        FooString = "Loaded";
    }

    // ##############################################################################################################################
    // PropertyChanged
    // ##############################################################################################################################

    #region PropertyChanged

    /// <summary>
    /// The PropertyChanged Eventhandler
    /// </summary>
    public event PropertyChangedEventHandler PropertyChanged;

    /// <summary>
    /// Raise/invoke the propertyChanged event!
    /// </summary>
    /// <param name="propertyName"></param>        
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    #endregion
}

解决方案1 ​​

订阅<Window x:Class="WpfApp1.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:local="clr-namespace:WpfApp1" mc:Ignorable="d" d:DataContext="{d:DesignInstance local:MainWindow}" Title="MainWindow" Height="450" Width="800"> <Grid> <TextBlock Text="{Binding Path=TestString}" VerticalAlignment="Center" HorizontalAlignment="Center"/> </Grid> </Window> Foo.PropertyChanged并将其发送至event。

MainWindow.PropertyChanged

Answer 1

我可能还没有完全理解你想要的东西，但这里有一个数据绑定的工作示例，这与你的例子有点接近。

两个主要变化是：

1. 将datacontext设置为VM，而不是
背后的代码
2. 实际上给OnPropertyChanged提供正确触发刷新所需的参数，即属性的名称。

<强>结果：

<强> MainWindow.xaml

<Window x:Class="ListViewColor.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">

    <Grid>
        <TextBlock Text="{Binding Foo.FooString}" VerticalAlignment="Center" HorizontalAlignment="Center" Background="Aqua"/>
    </Grid>
</Window>

<强> MainWindow.xaml.cs

namespace ListViewColor
{
    public partial class MainWindow : Window
    {
        public FooClass Foo { get; } = new FooClass();

        public MainWindow()
        {
            DataContext = this;
            InitializeComponent();
            Loaded += _OnLoaded;
        }

        private async void _OnLoaded(object sender, RoutedEventArgs e)
        {
            await Task.Delay(1000);
            Foo.ChangeTheProperty();
        }
    }
}

<强> FooClass.cs

using System.ComponentModel;
using System.Runtime.CompilerServices;

public class FooClass : INotifyPropertyChanged
{
    private string _FooString = "Empty";
    public string FooString
    {
        get
        {
            return _FooString;
        }
        set
        {
            if (_FooString == value) return;
            _FooString = value;
            OnPropertyChanged();
        }
    }

    public void ChangeTheProperty()
    {
        FooString = "Loaded";
    }

    #region PropertyChanged
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
    #endregion
}

我希望有所帮助！