ItemsControl DataTemplate不绑定到下划线数据

Question

I am having a very difficult time trying to get this to two-way bind to the item in the collection. The strange thing here is that the control shows the label but when I type anything in the text box it doesn't set the underlining value. Can someone please tell me what I'm doing wrong here.

        <ItemsControl Grid.Row="0" Grid.RowSpan="2" ItemsSource="{Binding QueryObject.RequiredParameters}">
            <ItemsControl.ItemTemplate>
                <DataTemplate DataType="{x:Type queryModels:QueryObjectParameter}">
                    <Grid>
                        <Grid.RowDefinitions>
                            <RowDefinition Height="Auto"></RowDefinition>
                            <RowDefinition Height="Auto"></RowDefinition>
                        </Grid.RowDefinitions>
                        <Label Grid.Row="0" Content="{Binding Label}"></Label>
                        <TextBox Grid.Row="1" Text="{Binding Value, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"></TextBox>
                    </Grid>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>

I've tried these different types.

1. {Binding Path=Value, RelativeSource={RelativeSource Self} , Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}
2. {Binding XPath=DataContext.Value, RelativeSource={RelativeSource Self} , Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}
3. {Binding XPath=Value, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}} , Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}
4. {Binding Path=Value, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}} , Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}

Thank you for your help!

Edit: I have been asked to add a better example to this so I created a very easy example. Note: the underlining model is called, but it doesn't set the model in the ViewModel.

 public class MainWindowViewModel:INotifyPropertyChanged
 {

      public MainWindowViewModel()
      {
           PersonQuery = new PersonQuery();
           Command = new DelegateCommand(CommandAction);
      }

      private void CommandAction()
      {
           MessageBox.Show(PersonQuery.Parameters.First().ToString());
      }

      public DelegateCommand Command { get; set; }

      public PersonQuery PersonQuery { get; set; }

      public event PropertyChangedEventHandler PropertyChanged;

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

 public class Parameter
 {
      public Parameter(string label)
      {
           Label = label;
      }
      public string Label { get; set; }

      public object Value { get; set; }

      public override string ToString()
      {
           return $"{Label}:{Value}";
      }
 }

 public class PersonQuery
 {
      public Parameter[] Parameters => new[] {new Parameter("Test"),};
 }

XAML:

    <Button Content="Run" Command="{Binding Command}"></Button>
    <ItemsControl Grid.Row="1" ItemsSource="{Binding PersonQuery.Parameters}">
        <ItemsControl.ItemTemplate>
            <DataTemplate DataType="{x:Type local:Parameter}">
                <Grid>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto"></RowDefinition>
                        <RowDefinition Height="Auto"></RowDefinition>
                    </Grid.RowDefinitions>

                    <Label Content="{Binding Label}"></Label>
                    <TextBox Grid.Row="1" Text="{Binding Value, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"></TextBox>
                </Grid>
            </DataTemplate>
        </ItemsControl.ItemTemplate>
    </ItemsControl>

Answer 1

Here's a simplified example where an ItemsControl is used and property update works both ways.

Simple Data class:

public class Data
{
    public int Id { get; set; }
    public string Name { get; set; }
}

Here I implemented INotifyPropertyChanged on my MainWindow for convenience, but you should really use a ViewModel and do this there.

public partial class MainWindow : Window, INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    protected void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    private ObservableCollection<Data> _dataList = null;
    public ObservableCollection<Data> DataList
    {
        get { return _dataList; }
        set
        {
            _dataList = value;
            OnPropertyChanged("DataList");
        }
    }

    public MainWindow()
    {
        InitializeComponent();
        DataList = new ObservableCollection<Data>
        {
            new Data() { Id = 1, Name = "Dan" },
            new Data() { Id = 2, Name = "Julie" }
        };

        DataContext = this;
    }
}

The XAML is super simple:

<ItemsControl ItemsSource="{Binding DataList}">
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <Grid Margin="5">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="100" />
                    <ColumnDefinition Width="100" />
                </Grid.ColumnDefinitions>
                <Label Grid.Column="0" Content="{Binding Id}"/>
                <TextBox Grid.Column="1" Text="{Binding Name, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
            </Grid>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

NOTE:

Check in your code if you have:

1. Implemented INotifyPropertyChanged
2. Use an ObservableCollection for your list.