WPF可觀察集合未更新

我是 WPF 環境中的新手，我一直在尋找解決方案，盡管我確定這只是我尚未理解的非常基本的東西

我正在嘗試使用 Observable 集合來更新 Listview 我在視圖模型中添加了一個方法，我需要從外部代碼呼叫以將另一個專案添加到串列中。

當我在除錯器打開的情況下在 ViewModel 中呼叫方法 addTask 時，我可以看到它在串列中計數了 1 個專案。但它不會將它添加到 ListView

模型：

    public class Tasks : INotifyPropertyChanged
{
    private string taskName;
    private string fromTime;
    private string toTime;
    private string message;
    private string taskCreator;

    public string TaskName
    {
        get
        {
            return taskName;
        }
        set
        {
            taskName = value;
            OnPropertyChanged("TaskName");
        }
    }
    public string FromTime
    {
        get
        {
            return fromTime;
        }
        set
        {
            fromTime = value;
            OnPropertyChanged("FromTime");
        }
    }
    public string ToTime
    {
        get
        {
            return toTime;
        }
        set
        {
            toTime = value;
            OnPropertyChanged("ToTime");
        }
    }
    public string Message
    {
        get
        {
            return message;
        }
        set
        {
            message = value;
            OnPropertyChanged("Message");
        }
    }
    public string TaskCreator
    {
        get
        {
            return taskCreator;
        }
        set
        {
            taskCreator = value;
            OnPropertyChanged("TaskCreator");
        }
    }
   
    

    #region INotifyPropertyChanged Members  

    public event PropertyChangedEventHandler PropertyChanged;
    private void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    #endregion

}

視圖模型：

    class TasksViewModel 
{


    public TasksViewModel()
    {
        
            {
            _UsersList.Add(new Tasks() { TaskName = "TaskName1", FromTime = "03:00", ToTime = "07:00", TaskCreator = "TaskCreator1", Message = "Hello" });
            _UsersList.Add(new Tasks() { TaskName = "TaskName2", FromTime = "03:00", ToTime = "07:00", TaskCreator = "TaskCreator2", Message = "Hello" });
            _UsersList.Add(new Tasks() { TaskName = "TaskName3", FromTime = "03:00", ToTime = "07:00", TaskCreator = "TaskCreator3", Message = "Hello" });

            
        };
    }

    public ObservableCollection<Tasks> Tasks
    {
        get { return _UsersList; }
        
       
    }
    public ObservableCollection<Tasks> _UsersList { get; set; } = new ObservableCollection<Tasks>();


    public void addTask(string taskName, string fromTime, string toTime, string taskCreator, string message) 
    {
        _UsersList.Add(new Tasks() { TaskName = taskName, FromTime = fromTime, ToTime = toTime, TaskCreator = taskCreator, Message = message });
       
    }

我要更新的串列視圖 (Xaml)

  <ListView Name="TaskGrid1" Grid.Row="1" Grid.Column="1" Margin="4,4,12,13"  ItemsSource="{Binding Tasks}" RenderTransformOrigin="0.5,0.5" FontSize="30" >
            <ListView.RenderTransform>
                <TransformGroup>
                    <ScaleTransform/>
                    <SkewTransform/>
                    <RotateTransform Angle="0"/>
                    <TranslateTransform/>
                </TransformGroup>
            </ListView.RenderTransform>
            <ListView.View>
                <GridView x:Name="List00000600">
                    <GridViewColumn Header="Tid" DisplayMemberBinding="{Binding FromTime}"  Width="100"/>
                    <GridViewColumn Header="Opgave" DisplayMemberBinding="{Binding TaskName}"  Width="350" />
                    <GridViewColumn Header="Opretter" DisplayMemberBinding="{Binding TaskCreator}" Width="120" />
                    
                </GridView>
            </ListView.View>
        </ListView>

uj5u.com熱心網友回復：

我不知道你是如何在 app.xaml 中分配視圖模型的。

只需打開 xaml 檔案，該檔案包含您的串列視圖并像往常一樣構建您的視窗：

<Window
    ... (rest of xmlns) 
    xmlns:MyViewModels="clr-namespace:YourViewModelNamespace"
>
    <Window.DataContext>
        <MyViewModels:TasksViewModel/>
    </Window.DataContext>
    <Grid/Or any container>         
        ...
        <ListView... />
    </Grid/Or any container
</Window>   

如前所述，將 _UserList 替換為 Tasks。

您的異步 TasksCreate() 正在創建 TasksViewModel 的新實體，因此它永遠不會更新當前實體。

PS：您可以通過以下方式獲取視圖模型：

// this function belongs to mainwindow/anywindow
public void CodeBehindClickEvent(object sender, RoutedEventArgs e)
{
    var VM = (TasksViewModel)this.DataContext;

    VM.addTask("blabla", ...)

    VM.TasksCreate();
}

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