MVVM C#WPF-在observablecollection中更改项目时未更新UI

我已经看了两天关于这个问题的Stackoverflow帖子了，我似乎不明白为什么我的代码不起作用

当我在

可观察集合

中更改项目时，我似乎无法更新UI中的数据网格

我知道，

ObservableCollection

不会触发

PropertyChanged

事件（如果其中的项目发生更改）

其他人似乎已经成功地做到了这一点，他们将

INotifyPropertyChanged

添加到模型中，并在属性更改时调用

OnPropertyChanged

。我已经实现了这个，并且检查了

PropertyChanged

事件是否正在发生

将新项目添加到集合时，UI将更新

testObj = modelObj

我意识到这可能是一个线程问题，但我真的不知道如何检查或修复它

我对编程相当陌生，并试图对MVVM了如指掌

有什么建议吗

型号：

public class ModelObj : INotifyPropertyChanged
{
    public string Name { get; set; }
    public string IpAddress { get; set; }

    private DateTime timer;

    public DateTime Timer
    {
        get { return timer; }
        set
        {
            timer = value;
            OnPropertyChanged();
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

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

public class MainViewModel : ViewModelBase
{
    public ObservableCollection<ModelObj> ModelObjects { get; } = new ObservableCollection<ModelObj>();

    private IUdpDataService _udpDataService;

    public MainViewModel(IUdpDataService udpDataService)
    {
        _udpDataService = udpDataService;
    }

    public void StartUdpDataService()
    {
        _udpDataService.StartBroadCasting();
        _udpDataService.ReceivedDataEvent += ParseReceivedData;
    }

    private void ParseReceivedData(string receivedData)
    {
        // This object contains all the information in the received data packet. 
        UdpPacket udpPacket = new UdpPacket(receivedData);

        // This object only contains the object name, IpAddress and a time variable.
        ModelObj modelObj = new ModelObj
        {
            Name = udpPacket.Name,
            IpAddress = udpPacket.IpEthernet,
            Timer = DateTime.Now,
        };

        App.Current.Dispatcher.Invoke((Action)delegate
        {
            UpdateList(modelObj);
        });
    }

    private void UpdateList(ModelObj modelObj)
    {
        var testObj = ModelObjects.FirstOrDefault(x => x.Name == modelObj.Name);
        if (testObj != null)
        {
            testObj = modelObj
        }
        else
        {
            ModelObjects.Add(modelObj);
            testObj = modelObj;
        }
    }
}

public partial class MainWindow : Window
{
    private MainViewModel _viewModel;

    public MainWindow(MainViewModel viewModel)
    {
        InitializeComponent();
        _viewModel = viewModel;
        DataContext = _viewModel;
        Loaded += MainWindow_Loaded;
    }

    private void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        _viewModel.StartUdpDataService();
    }

    protected override void OnClosing(System.ComponentModel.CancelEventArgs e)
    {
            Settings.Default.Save();
            base.OnClosing(e);
    }
}

     <DataGrid Grid.Row="0" ItemsSource="{Binding Path=ModelObjects}"
              IsReadOnly="True"
              Background="white"
              RowHeaderWidth ="0" 
              AutoGenerateColumns="False">

        <DataGrid.Columns>
            <DataGridTextColumn Header="Name" Binding="{Binding Name}" Width="auto" MinWidth="150"/>
            <DataGridTextColumn Header="IP address" Binding="{Binding IpAddress}" Width="*"/>
            <DataGridTextColumn Header="Timer" Binding="{Binding Timer, UpdateSourceTrigger=PropertyChanged}" Width="*"/>
        </DataGrid.Columns>
    </DataGrid>

视图模型：

public class ModelObj : INotifyPropertyChanged
{
    public string Name { get; set; }
    public string IpAddress { get; set; }

    private DateTime timer;

    public DateTime Timer
    {
        get { return timer; }
        set
        {
            timer = value;
            OnPropertyChanged();
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

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

public class MainViewModel : ViewModelBase
{
    public ObservableCollection<ModelObj> ModelObjects { get; } = new ObservableCollection<ModelObj>();

    private IUdpDataService _udpDataService;

    public MainViewModel(IUdpDataService udpDataService)
    {
        _udpDataService = udpDataService;
    }

    public void StartUdpDataService()
    {
        _udpDataService.StartBroadCasting();
        _udpDataService.ReceivedDataEvent += ParseReceivedData;
    }

    private void ParseReceivedData(string receivedData)
    {
        // This object contains all the information in the received data packet. 
        UdpPacket udpPacket = new UdpPacket(receivedData);

        // This object only contains the object name, IpAddress and a time variable.
        ModelObj modelObj = new ModelObj
        {
            Name = udpPacket.Name,
            IpAddress = udpPacket.IpEthernet,
            Timer = DateTime.Now,
        };

        App.Current.Dispatcher.Invoke((Action)delegate
        {
            UpdateList(modelObj);
        });
    }

    private void UpdateList(ModelObj modelObj)
    {
        var testObj = ModelObjects.FirstOrDefault(x => x.Name == modelObj.Name);
        if (testObj != null)
        {
            testObj = modelObj
        }
        else
        {
            ModelObjects.Add(modelObj);
            testObj = modelObj;
        }
    }
}

public partial class MainWindow : Window
{
    private MainViewModel _viewModel;

    public MainWindow(MainViewModel viewModel)
    {
        InitializeComponent();
        _viewModel = viewModel;
        DataContext = _viewModel;
        Loaded += MainWindow_Loaded;
    }

    private void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        _viewModel.StartUdpDataService();
    }

    protected override void OnClosing(System.ComponentModel.CancelEventArgs e)
    {
            Settings.Default.Save();
            base.OnClosing(e);
    }
}

     <DataGrid Grid.Row="0" ItemsSource="{Binding Path=ModelObjects}"
              IsReadOnly="True"
              Background="white"
              RowHeaderWidth ="0" 
              AutoGenerateColumns="False">

        <DataGrid.Columns>
            <DataGridTextColumn Header="Name" Binding="{Binding Name}" Width="auto" MinWidth="150"/>
            <DataGridTextColumn Header="IP address" Binding="{Binding IpAddress}" Width="*"/>
            <DataGridTextColumn Header="Timer" Binding="{Binding Timer, UpdateSourceTrigger=PropertyChanged}" Width="*"/>
        </DataGrid.Columns>
    </DataGrid>

XAML:

public class ModelObj : INotifyPropertyChanged
{
    public string Name { get; set; }
    public string IpAddress { get; set; }

    private DateTime timer;

    public DateTime Timer
    {
        get { return timer; }
        set
        {
            timer = value;
            OnPropertyChanged();
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

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

public class MainViewModel : ViewModelBase
{
    public ObservableCollection<ModelObj> ModelObjects { get; } = new ObservableCollection<ModelObj>();

    private IUdpDataService _udpDataService;

    public MainViewModel(IUdpDataService udpDataService)
    {
        _udpDataService = udpDataService;
    }

    public void StartUdpDataService()
    {
        _udpDataService.StartBroadCasting();
        _udpDataService.ReceivedDataEvent += ParseReceivedData;
    }

    private void ParseReceivedData(string receivedData)
    {
        // This object contains all the information in the received data packet. 
        UdpPacket udpPacket = new UdpPacket(receivedData);

        // This object only contains the object name, IpAddress and a time variable.
        ModelObj modelObj = new ModelObj
        {
            Name = udpPacket.Name,
            IpAddress = udpPacket.IpEthernet,
            Timer = DateTime.Now,
        };

        App.Current.Dispatcher.Invoke((Action)delegate
        {
            UpdateList(modelObj);
        });
    }

    private void UpdateList(ModelObj modelObj)
    {
        var testObj = ModelObjects.FirstOrDefault(x => x.Name == modelObj.Name);
        if (testObj != null)
        {
            testObj = modelObj
        }
        else
        {
            ModelObjects.Add(modelObj);
            testObj = modelObj;
        }
    }
}

public partial class MainWindow : Window
{
    private MainViewModel _viewModel;

    public MainWindow(MainViewModel viewModel)
    {
        InitializeComponent();
        _viewModel = viewModel;
        DataContext = _viewModel;
        Loaded += MainWindow_Loaded;
    }

    private void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        _viewModel.StartUdpDataService();
    }

    protected override void OnClosing(System.ComponentModel.CancelEventArgs e)
    {
            Settings.Default.Save();
            base.OnClosing(e);
    }
}

     <DataGrid Grid.Row="0" ItemsSource="{Binding Path=ModelObjects}"
              IsReadOnly="True"
              Background="white"
              RowHeaderWidth ="0" 
              AutoGenerateColumns="False">

        <DataGrid.Columns>
            <DataGridTextColumn Header="Name" Binding="{Binding Name}" Width="auto" MinWidth="150"/>
            <DataGridTextColumn Header="IP address" Binding="{Binding IpAddress}" Width="*"/>
            <DataGridTextColumn Header="Timer" Binding="{Binding Timer, UpdateSourceTrigger=PropertyChanged}" Width="*"/>
        </DataGrid.Columns>
    </DataGrid>

---

您应该设置现有对象的

计时器

属性：

private void UpdateList(ModelObj modelObj)
{
    var testObj = ModelObjects.FirstOrDefault(x => x.Name == modelObj.Name);
    if (testObj != null)
    {
        testObj.Timer = modelObj.Timer
    }
    else
    {
        ModelObjects.Add(modelObj);
    }
}

您当前正在获取对现有对象的引用，然后将保存此引用的

testObj

变量设置为对传递给

UpdateList

方法的新

ModelObj

对象的引用。这不会更新ModelObjects集合中对象的

Timer

属性

testObj = modelObj

没有效果。您只需在变量中输入一个值。召唤

    if (testObj != null)
    {
        ModelObjects.Replace(testObj,modelObj)
    }
    else
    {
        ModelObjects.Add(modelObj);
    }

---

如果您替换整个对象，则根本不需要实现INotifyPropertyChanged

他并不是只更新Timer，据我所知，他希望替换整个对象（因此新的ipAddress和其他字段也将在其中），只有Timer属性引发PropertyChanged事件。此外，他正在根据名称将modelObj映射到testObj，因此这不太可能更改。谢谢！愚蠢的错误，但oldObj=newObj会“移动”属性值，然后触发propertychanged事件。@AndréNicolaysen此代码不同，它不会像初始代码那样复制IpAddress。但是，如果更改单元格中的值，则目标是错误的，

。只有在正在编辑的单元格失去焦点（单击另一个单元格）时，才会触发PropertyChanged

，您可能希望实现

INotifyPropertyChanged

和

INotifyPropertyChanged